How to add an annotation in code behind at run time in WPF PDF Viewer?

The WPF PDF Viewer allows you to add an annotation to the PDF document at runtime in the User Interface (UI) and also from the code behind. We can add the annotation to the PDF document with the help of the PdfViewerControl’s loadedDocument property from the code behind.

Steps to add annotation in code behind at runtime:

The below steps illustrate how to add the ink annotation at runtime to the PDF document in the code behind.

1. Get the instance of the loaded document from the PdfViewerControl.

C#

//Get the loadedDocument from the PDF Viewer
PdfLoadedDocument loadedDocument = pdfViewer.LoadedDocument;

2. Create an ink annotation with a list of ink points.

C#

//Specify the ink points
List<float> inkPoints = new List<float> { 40, 300, 60, 100, 40, 50, 40, 300 };
 
//Specify the bounds of an annotation
RectangleF rectangle = new RectangleF(0, 0, 300, 400);
 
//Create a new ink annotation
PdfInkAnnotation inkAnnotation = new PdfInkAnnotation(rectangle, inkPoints);

3. Add the ink annotation to the desired page of the PdfLoadedDocument property instance.

C#

//Add annotation to the page
loadedDocument.Pages[0].Annotations.Add(inkAnnotation);

Now, the added annotation will be visible in the PDFViewer UI. Similarly, we can add other annotations to the PDF document at runtime in the PDF Viewer through the code behind it.

View the Sample in GitHub

See also:

• Annotations in WPF PDF Viewer
• Adding annotations to a PDF document