Digitally signing pdf documents

General system Applications
1

I was wondering if anyone had found an aesthetically acceptable way to digitally sign PDF documents? Ideally this would include an image that somewhat resembles wet ink signature.

Okular on KDE supports digital signatures but the output is ugly and graphical signatures are basically unsupported. DocuSign is cross platform, and while the signatures look cleaner and more professional it is cloud based and isn’t FOSS…

2

Hmm this does appear to be trickier than I’d assumed. I’ll have to do some more digging, I’ve just been using my work computer since it’s all setup for signing using Adobe.

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3

I recently heard about StirlingPDF but haven’t tried it out yet.

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4

Are you talking about

  1. digital signatures that are a type of electronic signature that uses a certificate-based digital ID, or
  2. conventional digital handwritten signatures, input either as image or by “Stylus”-pen?

If its the second, I would suggest opening the PDF in Xournal++ (install with sudo pacman -S xournalpp) and either insert and place and resize an image of your signature, or if you have a graphics tablet or a touchscreen with pen input, easily input your signature as vector overlay wherever you want in the pdf.
You can then export as a new PDF with your signature. If you need to flatten the pdf just print to pdf with cups-pdf.

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5

Actually it is both. I want to digitally sign PDFs with a cryptographic key and also include a wet-ink style signature. The problem is that anybody who has received a signed document from me can forge my signature, but digital signatures from FOSS PDF apps look ugly/unprofessional. DocuSign offers the benefits of both but it is proprietary.

6

I unfortunately don’t have any experience with these, but have you ever tried

  1. pyHanko (seems to be quite customizable, see pyHanko documentation) or
  2. LibreOffice (see LibreOffice help)