Sign PDF Documents, Office File API
Digital Signature Algorithm (DSA) in Cryptography: A Complete Guide
A Guide for Digitally Signing PDF Files in C#, by Andrew Wilson
Digitally Sign and Verify Signatures in PDF Files Using C#: A Complete Guide
How Digital Signatures Work
c# - How to verify that a pdf file contains a valid digital signature? - Stack Overflow
Adobe PDF Digital ID Signature
Digitally Sign and Verify Signatures in PDF Files Using C#: A Complete Guide
certificates - How to programatically verify a file signature? - Information Security Stack Exchange
Digitally Sign and Verify Signatures in PDF Files Using C#: A Complete Guide