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Example of Invisible Signature in ASP.NET Core PDF Viewer Control

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.

  • This message appears if the digitally signed document is edited after reloading.

2. The document has been digitally signed and at least one signature has a problem.

  • This message is shown if the digital signature is not registered on the machine and is not in the trusted list. Adding the certificate to the trusted list is necessary.

3. The document has been digitally signed and all the signatures are valid.

  • This message indicates that the document is digitally signed without any issues.

More information on the PDF Viewer instantiation can be found on this documentation section .

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