Digital signatures in webform2pdf through TCPDF

webform2pdf makes use of TCPDF, which has support for digital signatures.

I am pondering on how that potential can be leveraged in this module so that we can generate signed PDF files?

Two example cases:
a) Server signs with timestamp, server name / url / logo, etc., which involves some server-side magic.
b) User signs with personal digital signature (also receives timestamp inside the signature area, etc.), which implies client-side software handling the "private key" part and authentication (password to use the private key).