# Logical Structure

This article describes the logical structure of **RadPdfViewer**.

## RadFixedDocument

When **LoadDocument** finishes loading a document, a new **RadFixedDocument** instance is created. **RadFixedDocument** is the class that represents logically a single PDF document inside RadPdfViewer. The members that **RadFixedDocument** exposes are:

* **Pages**: A collection of **RadFixedPage** items created for the current document in the viewer.

* **Selection**: Information about the current selection in the document.

* **Annotations**: A collection of all annotations (such as links) in the current document.

* **Destinations**: A collection of all destinations (roughly said “bookmarks”) in the document that have links to them.

* **CaretPosition**: The current position of the caret.

#### Document information

**RadFixedDocument** exposes a **DocumentInfo** property of type **RadFixedDocumentInfo**, intended to hold additional information about the document. The RadFixedDocumentInfo class allows to set the following properties:

* **Author**: The author of the document.
* **Title**: The title of the document.
* **Description**: Text that describes the content of the document.

Other useful properties that **RadFixedDocument** exposes:

* **Bookmarks**: Gets the bookmarks.
* **Annotations**: Gets the annotations.
* **PageMode**: Gets or sets the PageMode.
* **HasLayers**: This property indicates whether the document contains layers.

For more details about the model used by PdfViewer and the members of [RadFixedDocument](https://docs.telerik.com/devtools/document-processing/libraries/radpdfprocessing/model/radfixeddocument), check the documentation of [PdfProcessing library](https://docs.telerik.com/devtools/document-processing/libraries/radpdfprocessing/overview).

## RadFixedPage

**RadFixedPage** represents logically a single page of a document. The **Pages** collection of RadFixedDocument consists of such objects and they are used as data items by the virtualized **RadFixedPageElement**.

For more details about the [RadFixedPage](https://docs.telerik.com/devtools/document-processing/libraries/radpdfprocessing/model/radfixedpage), check the documentation of [PdfProcessing library](https://docs.telerik.com/devtools/document-processing/libraries/radpdfprocessing/overview).

## See Also

* [Visual Structure](https://www.telerik.com/products/winforms/documentation/controls/pdfviewer/structure/visual-structure)
* [Design Time](https://www.telerik.com/products/winforms/documentation/controls/pdfviewer/design-time)
* [Getting Started](https://www.telerik.com/products/winforms/documentation/controls/pdfviewer/getting-started)