This sample demonstrates how to digitally sign a PDF document from code behind using Syncfusion's PDF Viewer and PDF Library
This sample operates correctly when a signature field is present in the PDF document. If all signature fields are signed, the "Finish Signing" button becomes enabled. Clicking this button adds a digital signature certificate programmatically and reloads the digitally signed document into the viewer.
The below are the messages shown in the respective scenarios:
1. The document has been digitally signed, but it has been modified since it was signed and at least one signature is invalid.
2. The document has been digitally signed and at least one signature has a problem.
3. The document has been digitally signed and all the signatures are valid.
More information on the PDF Viewer instantiation can be found on this documentation section .