How to Include Popup Annotation in PDF document using PDF Viewer in Windows Forms?

Currently, there is no support to include pop-up annotation in Windows Forms using the PdfViewerControl. However, the following workaround has the support for the same action in Windows Forms.

C#

 //Create a new popup annotation
 PdfPopupAnnotation popupAnnotation = new PdfPopupAnnotation(bounds, textBox.Text);
 
 // Set the location
 popupAnnotation.Location =new System.Drawing.PointF(Point.X,  Point.Y);
 
 // Set the properties
 popupAnnotation.Border.Width = 4;
 
 //Set the pdf popup icon
 popupAnnotation.Icon = PdfPopupIcon.Note;
 
 //Add this annotation to a new page
 ldoc.Pages[currentPageIndex].Annotations.Add(popupAnnotation);
 

Sample:

https://www.syncfusion.com/downloads/support/directtrac/general/ze/PdfViewerPopup766861027 

Steps to be followed: 

1. Drag the text box control, which is available at the left to the displayed document at the required position. 
2. Using the text box, you can enter and edit the text and also move and delete the text box control. 
3. To save the annotations in the document, go to File, and click Save. It will save the text as PopupAnnotation on the saved PDF file in the Output folder. 
4. To open a new document, go to File, and click Save.