Sign/Verify documents(ex. PDF) using Duniter private keys

I was looking at https://forum.duniter.org/t/utiliser-la-toile-de-confiance-pour-signer-des-messages/2964/14 but nothing came out.

Is there a way to use Duniter private key's (like in Pubsec or WIF or EWIF format, etc) to sign a document like for exemple PDF as sometimes we are forced to do with our personal gvt digital certificate signature?

Also besides signing it would be cool to verify a signature in a file.

Or is this already possible with some external tool besides Silkaj? Seems that https://pypi.org/project/duniterpy/ already supports it but just as messages, maybe we need to convert to base64 the file.

THanks.