How do I check if PDF signature is valid ?

[Support]

Q:

I am working in a project that creates signatures and digitally signs PDF.  I am very pleased with PDFNet SDK because I found doing it very simple, but now I would like to validate PDF signatures .... same as Acrobat does (the document has not changed since it was signed).

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A:

Besides signing documents, PDFNet can be also used to extract all relevant signature data.  For example:

https://groups.google.com/d/msg/pdfnet-sdk/QCEwoMmp3xk/BUYsS13u2kIJ

https://groups.google.com/d/msg/pdfnet-sdk/Oy0DWhdlYPU/BTx64lxaARYJ

https://groups.google.com/forum/#!tags/pdfnet-sdk/sign

 

… however it does not validate them against Adobe Approved Trust List (AATL), which is what Acrobat is doing. The list is subject to change from one version to another and validation requires internet connection. Most of our clients use their own trust lists or use custom signature workflows and validation. So although PDFNet will give you access to all info that you need to ‘validate’ PDF, it does not do this out of the box. If there is sufficient interest for built-in AATL validation we may add it in future.