Linux – How to verify a digital signature on a PDF on Linux

digital-signaturelinuxpdf

I am a Linux desktop user.

Someone sends me a PDF file which is digitally signed. It is supposed to be signed using some kind of government / regulated body / official institution issued certificate.

Is there a way that I, as a typical end-user, could determine whether the signature is valid?

I know Windows Acrobat Reader works to some extend, though even there it's not really clear about the validity of a signature as opposed to the fact that it's there and seems to be from XYZ.

Best Answer

I spent few hours experimenting with that and found that:

1) pdfsig command from poppler-utils package is able to validate PDF signature. Usage is simple: 

pdfsig signed.pdf

But for me it works only for visible signatures (version 0.62.0 on Fedora 28). For invisible signatures it shows:

File 'signed.pdf' does not contain any signatures

2) Master PDF Editor is a GUI tool which shows and validates signatures as shown on the picture below and it is enough to have free version. Master PDF Editor - Signatures

3) LibreOffice Draw is able to show and validate signature using File -> Electronic signatures -> Electronic signatures. But in my case it again shows only visible signatures.

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