I couldn't find in the questions a tool that adds digital signatures to a .pdf file via the linux command.
I need a tool that adds digital certificate to .df files
I have the .pfx certificate
Check this out : https://github.com/jmarxuach/BatchPDFSign
BatchPDFSign is a jar command line to sign PDF file with a PKCS12 certificate.
To use it you need a PKCS12 certificate. It should be a .pfx file. The password for the .pfx and a PDF file to sign.