PortableSigner is a signing (with X.509 certificates) program for
PDF files. It's platform independent and runs (tested) under
Windows (2000, XP, ...), Linux and Mac OS X.

It's possible to sign PDF documents digital with X.509 certificates.
This signed documents are read only. Therefore it's possible to
implement "electronic paper".

Homepage:
https://portablesigner.sourceforge.net/
