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Signing a document with a digital signature
Updated on Feb 19, 2026
| Product Version | Product | Author |
|---|---|---|
| R1 2022 Service Pack 1 | RadPdfProcessing | Martin Velikov |
Description
How to sign a document with a digital signature using FixedContentEditor.
Solution
In order to sign a PDF file with the PdfProcessing library, you need an instance of the System.Security.Cryptography.X509Certificates.X509Certificate2 class. One way to create such an instance is to provide the path to a PFX file and the password in an X509Certificate2 constructor, as in the provided example.
csharp
PdfFormatProvider provider = new PdfFormatProvider();
RadFixedDocument document = ImportDocument();
string certificateFilePath = "Resources/JohnDoe.pfx";
string certificateFilePassword = "johndoe";
// Define the certificate which will be used for the signing.
X509Certificate2 certificate =
new X509Certificate2(certificateFilePath, certificateFilePassword);
// The name of the signature must be unique.
string signatureName = "SampleSignature";
// This is the Form XObject element that represents the contents of the signature field.
Form form = new Form();
form.FormSource = new FormSource();
form.FormSource.Size = new Size(120, 120);
// We will use the editor to fill the Form XObject.
FixedContentEditor formEditor = new FixedContentEditor(form.FormSource);
formEditor.DrawCircle(new Point(50, 50), 20);
formEditor.DrawText(signatureName);
// The Signature object is added to a signature field, so we can add a visualization to it.
SignatureField signatureField = new SignatureField(signatureName);
signatureField.Signature = new Signature(certificate);
// The widget contains the Form XObject and defines the appearance of the signature field.
SignatureWidget widget = signatureField.Widgets.AddWidget();
widget.Rect = new Rect(new Point(200, 600), new Size(100, 100));
widget.Border = new AnnotationBorder(100, AnnotationBorderStyle.Solid, null);
widget.Content.NormalContentSource = form.FormSource;
// The Widget class inherits from Annotation. And, as any other annotation, must be added to the respective collection of the page.
RadFixedPage page = document.Pages.AddPage();
page.Annotations.Add(widget);
document.AcroForm.FormFields.Add(signatureField);
// Add Signature flags
document.AcroForm.SignatureFlags = SignatureFlags.AppendOnly;
However, there are other approaches provided by the .Net Framework API that allow you to get an X509Certificate2 class instance. The following code snippet demonstrates a possible approach for getting an X509Certificate2 class instance from an external device (e.g. USB token or hardware security module (HSM)) using .Net Framework API:
csharp
X509Store store = new X509Store(StoreLocation.CurrentUser);
store.Open(OpenFlags.ReadOnly);
X509Certificate2Collection sel = X509Certificate2UI.SelectFromCollection(store.Certificates, null, null, X509SelectionFlag.SingleSelection);
X509Certificate2 cert = sel[0];