01 Dec to 08 Dec 2025: highlights of the new online resources that we published last week.

Article: https://docs.telerik.com/devtools/document-processing/knowledge-base/fix-invalid-license-watermark-and-framework-mismatch-telerik-document-processing
Summary: Learn how to diagnose and fix “Invalid product license” watermarks and framework mismatch errors when using Telerik Document Processing (PdfProcessing, WordsProcessing, SpreadProcessing). Ensure you aren’t mixing trial and commercial builds or .NET Framework binaries with .NET Standard/.NET binaries, and keep all Telerik.Documents.* and Telerik.Zip references on the same version aligned to your target framework. Reinstall from the correct NuGet feed, replace any legacy Telerik.Windows.Documents.* references, clear bin/obj and NuGet caches, then rebuild to remove the watermark and resolve load/runtime errors.

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24 Nov to 01 Dec 2025: highlights of the new online resources that we published last week.

Article: https://docs.telerik.com/devtools/document-processing/knowledge-base/registering-custom-font-variations-pdf-processing
Summary: Register custom font variations in RadPdfProcessing by mapping FontFamily, FontStyle, and FontWeight to specific TTF/OTF files via FontsRepository.RegisterFont, ensuring the correct face is embedded in your PDFs. The article explains the supported style/weight pairs (Normal/Bold and Normal/Italic) and shows how to route other weights like Light or SemiBold to those mappings using FontFileSource.

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10 Nov to 17 Nov 2025: highlights of the new online resources that we published last week.

Summary: This changelog provides versioned release notes for the Telerik Document Processing AI Coding Assistant, including dates, new features, enhancements, and fixes. Use it to track changes and compatibility, plan upgrades, and troubleshoot behavior across versions in your projects.

Article: https://docs.telerik.com/devtools/document-processing/knowledge-base/changing-date-format-exported-excel-blazor-grid
Summary: Explains how to change the date format in an Excel export from a Telerik UI for Blazor Grid by post-processing the generated workbook with Telerik Document Processing (SpreadProcessing). You handle the grid’s Excel export event, target DateTime columns or cells in the worksheet, and apply a CellValueFormat/NumberFormat (e.g., yyyy-MM-dd) so Excel displays consistent date values instead of locale-specific text or serial numbers.

Article: https://docs.telerik.com/devtools/document-processing/libraries/radspreadprocessing/features/gen-ai-powered-document-insights/complete-context-question-processor
Summary: This article explains how to use the RadSpreadProcessing Gen‑AI Complete Context Question Processor to answer natural-language questions over a workbook using the full spreadsheet context (cells, evaluated formulas, named ranges, tables, charts, and pivot tables). It covers configuring LLM and embeddings providers, building the document context/index from a Workbook, and invoking the API to get answers with cell/range citations, plus options for scope control, retrieval depth, and token limits.

Article: https://docs.telerik.com/devtools/document-processing/knowledge-base/consistent-pdf-font-formatting
Summary: This article shows how to achieve consistent PDF font formatting when exporting with Telerik Document Processing (PdfProcessing/WordsProcessing). You register the complete font family (regular, bold, italic, bold-italic) via FontsRepository/FontsSettings, configure PdfExportSettings to embed fonts, and set explicit substitution/fallback fonts to avoid viewer-dependent faux styles and glyph fallback. These steps prevent mismatched fonts, weights, and glyphs across machines and PDF viewers.

Article: https://docs.telerik.com/devtools/document-processing/libraries/radspreadprocessing/features/gen-ai-powered-document-insights/custom-partialcontextquestionprocessor
Summary: This article shows how to implement and register a custom PartialContextQuestionProcessor in RadSpreadProcessing GenAI Document Insights to control partial context extraction from spreadsheets. You define logic to select relevant worksheets, ranges, tables, or metadata, override the context-building methods, and configure InsightsOptions so only the needed cells are sent to the LLM.

Article: https://docs.telerik.com/devtools/document-processing/libraries/radwordsprocessing/editing/gen-ai-powered-document-insights/custom-partialcontextquestionprocessor
Summary: This article shows how to implement a custom PartialContextQuestionProcessor in Telerik Document Processing (RadWordsProcessing) to control document context extraction for question answering and to tailor LLM prompt composition and token limits. It details the overrides and wiring to register the processor in the Gen-AI Document Insights pipeline and use it with OpenAI or Azure OpenAI providers.

Article: https://docs.telerik.com/devtools/document-processing/libraries/radpdfprocessing/features/gen-ai-powered-document-insights/custom-partialcontextquestionprocessor
Summary: This article shows you how to implement and register a custom PartialContextQuestionProcessor in RadPdfProcessing’s Gen AI–powered Document Insights to control which PDF segments are selected and sent to an LLM. You’ll learn how to plug in your own retrieval and prompt-building logic, tune context size and relevance filtering, and integrate the processor into the Document Insights workflow to tailor PDF question answering to your model and token budget.

Article: https://docs.telerik.com/devtools/document-processing/libraries/radpdfprocessing/features/digital-signature/external-digital-signing
Summary: RadPdfProcessing supports external digital signing of PDFs, letting you compute the signing hash for a SignatureField, send it to an HSM or remote key service, and then embed the returned CMS/PKCS#7 signature to finalize the document. The article details the two-phase workflow, required API calls, ByteRange handling, and supported hash algorithms (e.g., SHA-256) for integrating external signers.

Article: https://docs.telerik.com/devtools/document-processing/knowledge-base/fit-multiline-text-stamp-annotation-radpdfprocessing
Summary: This article explains how to render multiline, wrapped text inside a Telerik Document Processing RadPdfProcessing StampAnnotation by creating a custom appearance stream and drawing the text with FixedContentEditor. It covers measuring text widths, breaking lines to fit the annotation’s rectangle, configuring font/margins/alignment, and assigning the Normal appearance so the stamp renders correctly in PDF viewers.

Article: https://docs.telerik.com/devtools/document-processing/libraries/radspreadprocessing/features/gen-ai-powered-document-insights/getting-started
Summary: This guide shows how to configure and use Gen AI Powered Document Insights in Telerik Document Processing (RadSpreadProcessing) to programmatically analyze workbook data and ask questions about spreadsheets. It covers setup steps—adding required packages, configuring an AI provider, and enabling insights for a workbook or worksheet—and demonstrates calling the API to return structured answers with references to cells and ranges. The article includes .NET code samples to initialize the service and run queries.

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29 Oct to 05 Nov 2025: highlights of the new online resources that we published last week.

Article: https://docs.telerik.com/devtools/document-processing/knowledge-base/alternating-row-color-in-pdf-tables
Summary: Implement alternating row colors (zebra striping) in PDF tables with Telerik RadPdfProcessing (PdfProcessing) in C# by setting row or cell background fills during table generation. Use the FixedContentEditor/Table API and the row index (e.g., row % 2) to differentiate header and data rows and apply consistent styling in a RadFixedDocument.

Article: https://docs.telerik.com/devtools/document-processing/knowledge-base/generate-pdf-with-headers-footers-from-separate-html-files
Summary: Learn how to generate a PDF with repeating headers and footers from separate HTML files using Telerik Document Processing (WordsProcessing) in C#. You import body, header, and footer HTML with HtmlFormatProvider into RadFlowDocument instances, copy the header/footer content into the target document’s Section.Headers/Footers, then export to PDF with PdfFormatProvider.

Article: https://docs.telerik.com/devtools/document-processing/getting-started/installation/generating-api-keys
Summary: This guide shows you how to generate and manage API keys in your Telerik account to authenticate against the private Telerik NuGet feed for installing Telerik Document Processing packages. You’ll create a key (with optional expiration), copy it, and configure it in nuget.config, Visual Studio, or the dotnet/nuget CLI for local development and CI/CD, including how to revoke or rotate keys when needed.

Article: https://docs.telerik.com/devtools/document-processing/knowledge-base/pdfprocessing-prevent-font-conversion-embedding-fonts
Summary: To stop Telerik Document Processing PdfProcessing from converting your text to a different font or to outlines, register your TrueType/OpenType fonts with FontsRepository (for example, via FontsRepository.RegisterFont) and enable embedding when you export the RadFixedDocument. The article shows the code you need to register and use custom fonts, how to control embedding via export settings, and what to do when a font’s licensing prevents embedding and triggers fallback or outline conversion.

Article: https://docs.telerik.com/devtools/document-processing/knowledge-base/read-folder-encrypted-archive
Summary: This article shows you how to read and extract a specific folder from a password‑protected ZIP using Telerik Document Processing ZipLibrary in .NET. You iterate archive entries that match the target folder path and provide decryption settings (password) when opening each entry to stream out the files, handling directory structure creation as needed.

Feel free to check them out and share your thoughts!

The Telerik Team

After upgrading the Telerik Document Processing libraries to version Q1 2025 the following error messages may occur:

* "The file or assembly cannot be loaded 'Telerik.Licensing.Runtime, Version=1.4.6.0, Culture=neutral, PublicKeyToken=token_here' or one of its dependencies. The system cannot find the specified file."

* "NU1101: Unable to find package Telerik.Licensing. No packages exist with this id in source(s): Telerik nuget. PackageSourceMapping is enabled, the following source(s) were not considered: Microsoft Visual Studio Offline Packages, nuget.org."

Issue Summary:

When previewing PDF documents using RadPdfView (Telerik UI for WPF), the logo positioned at the top-left corner of the page fails to render consistently across machines. While the rest of the document displays correctly, the logo either appears distorted or is missing entirely.

Environment:

• Control Used: RadPdfView (Telerik UI for WPF)
• Telerik Libraries:
  • Telerik.Windows.Documents.dll – Version 2023.1.315.45
  • Telerik.Windows.Documents.Core.dll – Version 2023.1.307.40
• Operating Systems Tested:
  • Windows 10 Pro: Logo appears stretched and centered
  • Windows 11 Pro (Version 25H2, OS Build 26200.6899): Logo is missing

Symptoms:

• The logo, embedded in the PDF and originally positioned at the top-left corner, does not render correctly in RadPdfView.
• The issue is isolated to RadPdfView; the same PDF displays the logo correctly in WebView2 and standard web browsers.

Troubleshooting Steps Taken:

• Verified that the logo is present when viewed in other PDF viewers.
• Tested across multiple machines using identical code and PDF files.

Temporary Workaround:
Using <wv2:WebView2> to preview the PDF resolves the issue, indicating that the problem is specific to RadPdfView’s rendering engine.

Request:
Please confirm whether this is a known issue with the specified Telerik versions and advise if a fix or recommended workaround is available to ensure consistent logo rendering in RadPdfView across platforms.

Note: Using .NET version 4.8

The contents of an uploaded .docx file is being cut-off when converted to .pdf file.

 

Code snippet:

Can someone confirm if this a Telerik side issue, or am I missing a setting or config?

 

Thanks!

Can someone help me figure out what is wrong here?  I'm getting ad horribly vague Null exception.

 

var docxProvider = new Telerik.Windows.Documents.Flow.FormatProviders.Docx.DocxFormatProvider();
var pdfProvider = new Telerik.Windows.Documents.Flow.FormatProviders.Pdf.PdfFormatProvider();
RadFlowDocument document = new RadFlowDocument();
byte[] docBytes = File.ReadAllBytes(path);

document = docxProvider.Import(docBytes);    ERROR HERE

var resultBytes = pdfProvider.Export(document);

File.WriteAllBytes(resultPath, resultBytes);

 

The document i'm trying to load contains tables and images within the tables (jpeg barcodes)

I have verified that pretty much every other tool i use can read the file without issue. 

The goal is ultimately to export the file as a PDF.

 

Error details:

{"Object reference not set to an instance of an object."}

   at Telerik.Windows.Documents.Flow.FormatProviders.Docx.Model.Elements.Document.ParagraphPropertiesElement.OnAfterRead(IDocxImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase`3.OnAfterRead(IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase.Read(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase.ReadChildElements(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase.Read(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase.ReadChildElements(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase.Read(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase.ReadChildElements(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase.Read(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase.ReadChildElements(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase.Read(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase.ReadChildElements(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Elements.OpenXmlElementBase.Read(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Parts.OpenXmlPartBase.Import(IOpenXmlReader reader, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.Model.Parts.OpenXmlPartBase.Import(Stream stream, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.OpenXmlImporter`1.ImportPartFromArchive(ZipArchiveEntry zipEntry, PartBase part, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.FormatProviders.OpenXml.OpenXmlImporter`1.Import(Stream input, IOpenXmlImportContext context)
   at Telerik.Windows.Documents.Flow.FormatProviders.Docx.DocxFormatProvider.ImportOverride(Stream input)
   at Telerik.Windows.Documents.Common.FormatProviders.FormatProviderBase`1.Import(Stream input)
   at Telerik.Windows.Documents.Common.FormatProviders.BinaryFormatProviderBase`1.Import(Byte[] input)
   at IVC_BIPS_Desktop.rfrmMain.ConverDocxToPdf(String path, String resultPath) in C:\Source\IVC Batch Instructions Printing\IVC_BIPS_Desktop\rfrmMain.cs:line 499

Hi,

i have added and image and some text inside the digital signature and and set them inside properly but when i set the position of the signature field before the signature field like i was showing in below screenshot 


above screenshot i have added the signature field placed the top of the Letter M but when i validate the signature manually but in output the signature field position is not correct as i set the above screenshot below is the screenshot that you can check the position of the signature field

i don't know whats strange can anyone help me this to get it out  

i am getting the Telerik.Windows.Documents.Fixed.Exceptions.NotSupportedImageFormatException: 'Not supported image format.'  this exception in below code can anyone have a solution for that 


// Load the existing PDF from the byte array using PdfFormatProvider
using (MemoryStream inputStream = new MemoryStream(inDocByte))
{
    // Create PdfFormatProvider and load the existing document
    PdfFormatProvider provider = new PdfFormatProvider();
    RadFixedDocument document = provider.Import(inputStream);

    int pageNo = (signInfo.DigitalSignPage() == 0 ? 1 : document.Pages.Count);

    // Path to the image (ensure this is correct)
    System.Drawing.Image signatureImage = null;
    if (signInfo.DigitalSignMode() == 2 && HttpContext.Current.Session["imagesyncfusion"] != null)
    {
        signatureImage = (System.Drawing.Image)HttpContext.Current.Session["imagesyncfusion"];
    }
    // Check if digital signature is needed
    if (signInfo.UseDigitalSign())
    {
        if ((signInfo.DigitalSignMode() == 1) || (signInfo.DigitalSignMode() == 2))
        {
            double signaturePositionLeft = (double)signInfo.DigitalSignLeftInPoints();
            double signaturePositionTop = (double)signInfo.DigitalSignTopInPoints();
            double signatureFieldWidth = (double)signInfo.DigitalSignWidthInPoints();
            double signatureFieldHeight = (double)signInfo.DigitalSignHeightInPoints();
            RadFixedPage radFixedPage = document.Pages[pageNo - 1];

            if (!string.IsNullOrEmpty(customSignatureDetails))
            {
                // Movable signature case: Adjust the signature field based on custom details
                signatureFieldWidth = signaturePositionLeft + (double)signInfo.DigitalSignWidthInPoints();
                signatureFieldHeight = signaturePositionTop + (double)signInfo.DigitalSignHeightInPoints();

                string[] separator = new string[] { "!_!" };
                string[] offsetArray = customSignatureDetails.Split(separator, StringSplitOptions.RemoveEmptyEntries);

                if (offsetArray.Length >= 9)
                {
                    float offsetLeft = returnFloatWithCultureValue(offsetArray[0]);
                    float offsetTop = returnFloatWithCultureValue(offsetArray[1]);
                    float docHeight = returnFloatWithCultureValue(offsetArray[2]);
                    float greenDivHeight = returnFloatWithCultureValue(offsetArray[3]);
                    float greenDivWidth = returnFloatWithCultureValue(offsetArray[4]);
                    float dpi_x = returnFloatWithCultureValue(offsetArray[6]);
                    float dpi_y = returnFloatWithCultureValue(offsetArray[7]);
                    pageNo = int.Parse(offsetArray[8]);

                    // Calculate positions for drawing the text div;
                    signaturePositionLeft = (offsetLeft / dpi_x) * 72;
                    signaturePositionTop = (offsetTop / dpi_y) * 72;
                    signatureFieldWidth = (greenDivWidth / dpi_y) * 72;
                    signatureFieldHeight = (greenDivHeight / dpi_x) * 72;
                }
            }
            else
            {
                // Non-movable case: Place the signature field in a fixed location
                radFixedPage = document.Pages[pageNo - 1];
                Tuple<double, double> k = null;

                if (signatureImage != null)
                {
                    k = calculateAspectRatioFit(signatureImage.Width, signatureImage.Height, signatureFieldWidth, signatureFieldHeight);
                    signatureFieldWidth = k.Item1;
                    signatureFieldHeight = k.Item2;
                }

                signaturePositionLeft = radFixedPage.Size.Height - (double)(signatureFieldWidth + signatureFieldHeight + 1);
                signaturePositionTop = signaturePositionTop + 1; // +1 For border size
                                                                 //pdfForm.FormSource.Size = new Telerik.Documents.Primitives.Size(signatureFieldWidth, signatureFieldHeight);
            }

            // Create a new form to place the signature field
            Form pdfForm = new Form();
            pdfForm.FormSource = new FormSource();
            FixedContentEditor editor = new FixedContentEditor(pdfForm.FormSource);
            pdfForm.FormSource.Size = new Telerik.Documents.Primitives.Size(signatureFieldWidth, signatureFieldHeight);

            // Drawing the image at the starting position (left side of the signature field)
            imageWidth = signatureFieldWidth / 2;  // Half the width for the image
            double imageHeight = signatureFieldHeight;  // Use full height of the signature field

            if (signatureImage != null)
            {
                using (MemoryStream ms = new MemoryStream())
                {
                    signatureImage.Save(ms, signatureImage.RawFormat);
                    ms.Position = 0;
                    editor.DrawImage(ms, new Telerik.Documents.Primitives.Size(imageWidth, imageHeight));
                }
            }

            // Prepare text to draw beside the signature image
            string textToDraw = $"Digitally signed by {certificate.FriendlyName} \nDate: {DateTime.Now:yyyy.MM.dd HH:mm:ss zzz} \nReason: {pdfSignature.Signature.Properties.Reason} \nLocation: {pdfSignature.Signature.Properties.Location}";

            // Set text width and calculate font size
            double textWidth = signatureFieldWidth - imageWidth;
            double fontSize = CalculateFontSize(signatureFieldWidth - 23, signatureFieldHeight, textToDraw);

            // Define the position for the text and draw it
            Telerik.Windows.Documents.Fixed.Model.Editing.Block textBlock = new Telerik.Windows.Documents.Fixed.Model.Editing.Block();
            double textPositionLeft = signaturePositionLeft;  // Adding a 5px gap after the image
            textBlock.TextProperties.FontSize = fontSize;
            textBlock.InsertText($"Digitally signed by {certificate.FriendlyName}");
            textBlock.InsertText($" Date: {DateTime.Now:yyyy.MM.dd HH:mm:ss zzz}");
            textBlock.InsertText($" Reason: {pdfSignature.Signature.Properties.Reason}");
            textBlock.InsertText($" Location: {pdfSignature.Signature.Properties.Location}");
            
            Rect boundingRect;
            if (signatureImage != null)
            {
                boundingRect = new Rect(imageWidth, 5, textWidth, signatureFieldHeight);
            }
            else
            {
                boundingRect = new Rect(textPositionLeft, 5, textWidth, signatureFieldHeight);
            }
            textBlock.Draw(editor, boundingRect);
            //editor.DrawBlock(textBlock);
            // Create the SignatureWidget and position it on the PDF page
            SignatureWidget signatureWidget = pdfSignature.Widgets.AddWidget();
            signatureWidget.Content.NormalContentSource = pdfForm.FormSource;
            signatureWidget.Rect = new Rect(signaturePositionLeft, 0, signatureFieldWidth, signatureFieldHeight);
            signatureWidget.RecalculateContent();

            // Add signature widget to the page and draw the content
            RadFixedPage pdfPage = document.Pages[pageNo - 1];
            FixedContentEditor pageEditor = new FixedContentEditor(pdfPage);
            pageEditor.Position.Translate(signaturePositionLeft , signaturePositionTop + 258.3824795800782);
            pageEditor.DrawForm(pdfForm.FormSource);

            // Add the signature field to the document's AcroForm
            document.AcroForm.FormFields.Add(pdfSignature);

        }

    }
    // Export the document to a byte array and return
    using (MemoryStream memoryStream = new MemoryStream())
    {

        Telerik.Documents.ImageUtils.ImagePropertiesResolver defaultImagePropertiesResolver = new Telerik.Documents.ImageUtils.ImagePropertiesResolver();
        Telerik.Windows.Documents.Extensibility.FixedExtensibilityManager.ImagePropertiesResolver = defaultImagePropertiesResolver;
        PdfExportSettings settings = new PdfExportSettings() { ImageQuality = ImageQuality.High };
        //PdfFormatProvider provider = new PdfFormatProvider();
        provider.ExportSettings = settings;
        provider.Export(document, memoryStream);
        outDocPdf = memoryStream.ToArray();
    }

public static void SignPDFSynfusion(SignatureInfo signInfo, byte[] inDocByte, Cert objCert, string customSignatureDetails, out byte[] outDocPdf)
{
    // Dimensions and positions for the signature field
    double signatureFieldWidth; // Width of the signature field
    double signatureFieldHeight;
    double signaturePositionLeft;
    double signaturePositionTop;
   
    // Getting TimeStamp Details from Database..
    TimeStampSettings objTimeStampSettings = new TimeStampSettings();
    TimeStampInfo objTimeStampInfo = (TimeStampInfo)objTimeStampSettings.GetTimeStamp();
    PfxSettings objPfxSettings = new PfxSettings();

    // Params to take account in the input
    bool displaySignature = Convert.ToBoolean(HttpContext.Current.Session["showSign"]);

    bool needTimeStamp = false;
    string TsaServerUrl = "";
    string TsaServerUser = "";
    string TsaServerPassword = "";
    string strPasswrd = string.Empty;
    double imageWidth = 0;

    if (objTimeStampInfo != null)
    {
        needTimeStamp = (bool)objTimeStampInfo.TimeStampNeeded;
        TsaServerUrl = objTimeStampInfo.TimeStampUrl;

        if ((bool)objTimeStampInfo.AuthNeeded)
        {
            TsaServerUser = objTimeStampInfo.UserName;
            strPasswrd = SecurQueryString.decryptQueryString(objTimeStampInfo.Password);
            TsaServerPassword = strPasswrd;
        }
    }
    // Load the certificate
    X509Certificate2 certificate = new X509Certificate2(objCert.CertArray, objCert.Password);

    // Create a SignatureField and assign the digital signature to it
    SignatureField pdfSignature = new SignatureField("SignatureField");
    pdfSignature.Signature = new Telerik.Windows.Documents.Fixed.Model.DigitalSignatures.Signature(certificate);

    // Set signature details
    string strNotAvailable = HttpContext.GetGlobalResourceObject("GlobalResources", "lblNotAvlbl").ToString();
    pdfSignature.Signature.Properties.Reason = strNotAvailable;
    pdfSignature.Signature.Properties.ContactInfo = strNotAvailable;
    pdfSignature.Signature.Properties.Location = strNotAvailable;

    // Create a new form to place the signature field
    Form pdfForm = new Form();
    pdfForm.FormSource = new FormSource();

    // Load the existing PDF from the byte array using PdfFormatProvider
    using (MemoryStream inputStream = new MemoryStream(inDocByte))
    {
        // Create PdfFormatProvider and load the existing document
        PdfFormatProvider provider = new PdfFormatProvider();
        RadFixedDocument document = provider.Import(inputStream);

        int pageNo = (signInfo.DigitalSignPage() == 0 ? 1 : document.Pages.Count);
        try
        {
            if (needTimeStamp)
            {
                //.TimeStampServer = new TimeStampServer(new Uri(TsaServerUrl), TsaServerUser, TsaServerPassword);
            }
        }
        catch (Exception ex)
        { }

        // Path to the image (ensure this is correct)
        System.Drawing.Image signatureImage = null;
        if (signInfo.DigitalSignMode() == 2 && HttpContext.Current.Session["imagesyncfusion"] != null)
        {
            signatureImage = (System.Drawing.Image)HttpContext.Current.Session["imagesyncfusion"];
        }
        //var signatureImage = (System.Drawing.Image)HttpContext.Current.Session["imagesyncfusion"];

        if (signInfo.UseDigitalSign())
        {
            if ((signInfo.DigitalSignMode() == 1) || (signInfo.DigitalSignMode() == 2))
            {
                signaturePositionLeft = (double)signInfo.DigitalSignLeftInPoints();
                signaturePositionTop = (double)signInfo.DigitalSignTopInPoints();
                signatureFieldWidth = (double)signInfo.DigitalSignWidthInPoints();
                signatureFieldHeight = (double)signInfo.DigitalSignHeightInPoints();
                RadFixedPage radFixedPage = document.Pages[pageNo - 1];
                if (!string.IsNullOrEmpty(customSignatureDetails))
                {
                    //Movable case:
                    signatureFieldWidth = signaturePositionLeft + (double)signInfo.DigitalSignWidthInPoints();
                    signatureFieldHeight = signaturePositionTop + (double)signInfo.DigitalSignHeightInPoints();

                    string[] separator = new string[] { "!_!" };
                    string[] offsetArray = customSignatureDetails.Split(separator, StringSplitOptions.RemoveEmptyEntries);

                    if (offsetArray.Length >= 9)
                    {
                        float offsetLeft = returnFloatWithCultureValue(offsetArray[0]);
                        float offsetTop = returnFloatWithCultureValue(offsetArray[1]);
                        float docHeight = returnFloatWithCultureValue(offsetArray[2]);
                        float greenDivHeight = returnFloatWithCultureValue(offsetArray[3]);
                        float greenDivWidth = returnFloatWithCultureValue(offsetArray[4]);
                        float dpi_x = returnFloatWithCultureValue(offsetArray[6]);
                        float dpi_y = returnFloatWithCultureValue(offsetArray[7]);
                        pageNo = int.Parse(offsetArray[8]);

                        // Calculate positions for drawing the text div;
                        signaturePositionLeft = (offsetLeft / dpi_x) * 72;
                        signaturePositionTop = (offsetTop / dpi_y) * 72;
                        signatureFieldWidth = (greenDivWidth / dpi_y) * 72;
                        signatureFieldHeight = (greenDivHeight / dpi_x) * 72;

                        pdfForm.FormSource.Size = new Telerik.Documents.Primitives.Size(signatureFieldWidth, signatureFieldHeight);

                    }
                }
                else
                {
                    //Non-movable case:
                    radFixedPage = document.Pages[pageNo - 1];
                    Tuple<double, double> k = null;

                    if (signatureImage != null)
                    {
                        k = calculateAspectRatioFit(signatureImage.Width, signatureImage.Height, signatureFieldWidth, signatureFieldHeight);
                        signatureFieldWidth = k.Item1;
                        signatureFieldHeight = k.Item2;
                    }

                    signaturePositionLeft = radFixedPage.Size.Height - (double)(signatureFieldWidth + signatureFieldHeight + 1);
                    signaturePositionTop = signaturePositionTop + 1; // +1 For border size
                    pdfForm.FormSource.Size = new Telerik.Documents.Primitives.Size(signatureFieldWidth, signatureFieldHeight);
                }
                FixedContentEditor editor = new FixedContentEditor(pdfForm.FormSource);
                // Drawing the image at the starting position (left side of the signature field)
                imageWidth = signatureFieldWidth / 2;  // Half the width for the image
                double imageHeight = signatureFieldHeight;  // Use full height of the signature field

                if (signatureImage == null)
                {

                }
                else
                {
                    // Create a memory stream to hold the image
                    using (MemoryStream ms = new MemoryStream())
                    {
                        // Save the image to the memory stream
                        signatureImage.Save(ms, signatureImage.RawFormat);

                        // Reset the stream position to the beginning
                        ms.Position = 0;

                        // Pass the memory stream to the DrawImage method
                        editor.DrawImage(ms, new Telerik.Documents.Primitives.Size(imageWidth, imageHeight));
                    }
                }
                string textToDraw = $"Digitally signed by {certificate.FriendlyName} \nDate: {DateTime.Now.ToString("yyyy.MM.dd HH:mm:ss zzz")} \nReason: {pdfSignature.Signature.Properties.Reason} \nLocation: {pdfSignature.Signature.Properties.Location}";
                // Set the width of the text area (remaining space after the image)
                double textWidth = signatureFieldWidth - imageWidth;
                double dsd = CalculateFontSize(textWidth, signatureFieldHeight, textToDraw);

                // Now, draw the text next to the image (on the right side), within the remaining space
                Telerik.Windows.Documents.Fixed.Model.Editing.Block textBlock = new Telerik.Windows.Documents.Fixed.Model.Editing.Block();
                double textPositionLeft = signaturePositionLeft + imageWidth;  // Adding a 5px gap after the image
                textBlock.TextProperties.FontSize = 8;
                textBlock.InsertText($"Digitally signed by {certificate.FriendlyName}");
                textBlock.InsertText($" Date: {DateTime.Now.ToString("yyyy.MM.dd HH:mm:ss zzz")}");
                textBlock.InsertText($" Reason: {pdfSignature.Signature.Properties.Reason}");
                textBlock.InsertText($" Location: {pdfSignature.Signature.Properties.Location}");
                Rect boundingRect = new Rect(textPositionLeft - 8, signaturePositionTop - 12, textWidth, signatureFieldHeight);
                textBlock.Draw(editor, boundingRect);

                // Create the SignatureWidget and position it on the PDF page
                SignatureWidget signatureWidget = pdfSignature.Widgets.AddWidget();
                signatureWidget.Content.NormalContentSource = pdfForm.FormSource;
                signatureWidget.Rect = new Rect(signaturePositionLeft, signaturePositionTop, signatureFieldWidth, signatureFieldHeight);
                signatureWidget.RecalculateContent();

                // Add content from the form to the page at the specified position
                RadFixedPage pdfPage = document.Pages[0];  // Assuming you're adding it to the first page
                FixedContentEditor pageEditor = new FixedContentEditor(pdfPage);
                pageEditor.Position.Translate(signaturePositionLeft, signaturePositionTop);
                pageEditor.DrawForm(pdfForm.FormSource);

                // Add the signature field to the document's AcroForm
                document.AcroForm.FormFields.Add(pdfSignature);
            }
        }

        // Use MemoryStream to capture the PDF output and return as a byte array
        using (MemoryStream memoryStream = new MemoryStream())
        {
            // Export the document to the memory stream as a PDF
            Telerik.Documents.ImageUtils.ImagePropertiesResolver defaultImagePropertiesResolver = new Telerik.Documents.ImageUtils.ImagePropertiesResolver();
            Telerik.Windows.Documents.Extensibility.FixedExtensibilityManager.ImagePropertiesResolver = defaultImagePropertiesResolver;
            var settings = new PdfExportSettings();
            settings.ImageQuality = ImageQuality.High;
            provider.ExportSettings = settings;
            provider.Export(document, memoryStream);
            // Return the byte array of the PDF
            outDocPdf = memoryStream.ToArray();
            //return memoryStream.ToArray(); // Return the byte array of the signed PDF
        }
    }
}
       private static double CalculateFontSize(double textWidth, double signatureFieldHeight, string text)
       {
           // Start with a base font size for better precision
           double baseFontSize = 12.0;  // Starting font size

           // Calculate width scale factor to adjust the font size based on text length
           double widthScaleFactor = textWidth / text.Length;
           double widthFontSize = baseFontSize * widthScaleFactor;

           // Calculate height scale factor to adjust the font size based on the number of lines
           int numLines = text.Split('\n').Length;
           double heightScaleFactor = signatureFieldHeight / (numLines * baseFontSize);
           double heightFontSize = baseFontSize * heightScaleFactor;

           // Return the smaller font size to fit both dimensions
           return Math.Min(widthFontSize, heightFontSize);
       }

       public static Tuple<double, double> calculateAspectRatioFit(double srcWidth, double srcHeight, double maxWidth, double maxHeight)
       {
           var ratio = Math.Min(maxWidth / srcWidth, maxHeight / srcHeight);
           return new Tuple<double, double>(srcWidth * ratio, srcHeight * ratio);
       }

firstly loading the document i have use 
  // Load the PDF document
  var provider = new PdfFormatProvider();
  var loadedDocument = provider.Import(inDocByte,null);

and after some functinality to export the document i have used below 

 Telerik.Documents.ImageUtils.ImagePropertiesResolver defaultImagePropertiesResolver = new Telerik.Documents.ImageUtils.ImagePropertiesResolver();
 Telerik.Windows.Documents.Extensibility.FixedExtensibilityManager.ImagePropertiesResolver = defaultImagePropertiesResolver;
 provider.Export(document, memoryStream, null);
 outDocPdf = memoryStream.ToArray();

what was the problem can you tell me the solution for that exception

Unable to cast object of type 'Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Types.PdfLiteralString' to type 'Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Types.PdfName'.

the below method i got the exception i don't know what's wrong  can  anyone tell me 
the exception is occurred in below line 
  // Create PdfFormatProvider and load the existing document
 PdfFormatProvider pdfFormatProvider = new PdfFormatProvider();
 RadFixedDocument document = pdfFormatProvider.Import(inputStream);


static byte[] GenerateSignedPdf(Cert objCert, byte[] inDocByte)
{
    // Dimensions and positions for the signature field
    int signatureFieldWidth = 200; // Width of the signature field
    int signatureFieldHeight = 50;
    int signaturePositionLeft = 10;
    int signaturePositionTop = 10;

    // Load the certificate
    X509Certificate2 certificate = new X509Certificate2(objCert.CertArray, objCert.Password);

    // Create a SignatureField and assign the digital signature to it
    SignatureField pdfSignature = new SignatureField("SignatureField");
    pdfSignature.Signature = new Telerik.Windows.Documents.Fixed.Model.DigitalSignatures.Signature(certificate);

    // Set signature details
    string strNotAvailable = HttpContext.GetGlobalResourceObject("GlobalResources", "lblNotAvlbl").ToString();
    pdfSignature.Signature.Properties.Reason = strNotAvailable;
    pdfSignature.Signature.Properties.ContactInfo = strNotAvailable;
    pdfSignature.Signature.Properties.Location = strNotAvailable;

    // Load the existing PDF from the byte array using PdfFormatProvider
    using (MemoryStream inputStream = new MemoryStream(inDocByte))
    {
        // Create PdfFormatProvider and load the existing document
        PdfFormatProvider pdfFormatProvider = new PdfFormatProvider();
        RadFixedDocument document = pdfFormatProvider.Import(inputStream);

        // Create a new form to place the signature field
        Form pdfForm = new Form();
        pdfForm.FormSource = new FormSource();
        pdfForm.FormSource.Size = new Telerik.Documents.Primitives.Size(signatureFieldWidth, signatureFieldHeight);
        FixedContentEditor editor = new FixedContentEditor(pdfForm.FormSource);

        // Path to the image (ensure this is correct)
        var signatureImage = (System.Drawing.Image)HttpContext.Current.Session["imagesyncfusion"];

        // Drawing the image at the starting position (left side of the signature field)
        int imageWidth = signatureFieldWidth / 2;  // Half the width for the image
        int imageHeight = signatureFieldHeight;  // Use full height of the signature field

        // Create a memory stream to hold the image
        using (MemoryStream ms = new MemoryStream())
        {
            // Save the image to the memory stream
            signatureImage.Save(ms, signatureImage.RawFormat);

            // Reset the stream position to the beginning
            ms.Position = 0;

            // Pass the memory stream to the DrawImage method
            editor.DrawImage(ms, new Telerik.Documents.Primitives.Size(imageWidth, imageHeight));
        }

        string textToDraw = $"Digitally signed by {certificate.FriendlyName} \nDate: {DateTime.Now.ToString("yyyy.MM.dd HH:mm:ss zzz")} \nReason: {pdfSignature.Signature.Properties.Reason} \nLocation: {pdfSignature.Signature.Properties.Location}";
        // Set the width of the text area (remaining space after the image)
        int textWidth = signatureFieldWidth - imageWidth;
        double dsd = CalculateFontSize(textWidth - 23, signatureFieldHeight, textToDraw);

        // Now, draw the text next to the image (on the right side), within the remaining space
        Telerik.Windows.Documents.Fixed.Model.Editing.Block textBlock = new Telerik.Windows.Documents.Fixed.Model.Editing.Block();
        int textPositionLeft = signaturePositionLeft + imageWidth;  // Adding a 5px gap after the image
        textBlock.TextProperties.FontSize = dsd;
        textBlock.InsertText($"Digitally signed by {certificate.FriendlyName}");
        textBlock.InsertText($" Date: {DateTime.Now.ToString("yyyy.MM.dd HH:mm:ss zzz")}");
        textBlock.InsertText($" Reason: {pdfSignature.Signature.Properties.Reason}");
        textBlock.InsertText($" Location: {pdfSignature.Signature.Properties.Location}");
        Rect boundingRect = new Rect(textPositionLeft - 8, signaturePositionTop - 12, textWidth, signatureFieldHeight);
        textBlock.Draw(editor, boundingRect);

        // Create the SignatureWidget and position it on the PDF page
        SignatureWidget signatureWidget = pdfSignature.Widgets.AddWidget();
        signatureWidget.Content.NormalContentSource = pdfForm.FormSource;
        signatureWidget.Rect = new Rect(signaturePositionLeft, signaturePositionTop, signatureFieldWidth, signatureFieldHeight);
        signatureWidget.RecalculateContent();

        // Add content from the form to the page at the specified position
        RadFixedPage pdfPage = document.Pages[0];  // Assuming you're adding it to the first page
        FixedContentEditor pageEditor = new FixedContentEditor(pdfPage);
        pageEditor.Position.Translate(signaturePositionLeft, signaturePositionTop);
        pageEditor.DrawForm(pdfForm.FormSource);

        // Add the signature field to the document's AcroForm
        document.AcroForm.FormFields.Add(pdfSignature);

        // Use MemoryStream to capture the PDF output and return as a byte array
        using (MemoryStream memoryStream = new MemoryStream())
        {
            // Export the document to the memory stream as a PDF
            pdfFormatProvider.Export(document, memoryStream);
            return memoryStream.ToArray(); // Return the byte array of the signed PDF
        }
    }
}