Digitally sign PDF files

[haxier]

Hi all

I'm developing an application with some reports and we're looking for
advice. This reports should be openoffice.org .odf files, pdf files,
and perhaps microsoft word files (.doc, .docx?) and must be digitally
signed. Is out there some kind of libraries to ease this tasks?

* Access to the local user certificate store, and read PEM or PKCS12
certificate files.
* Read, parse and validate user certificates
* Sign documents: as a binary stream, within an specific document
(pdf, odt, doc)

I've been googling and found very few documentation about this --
except some examples using jython and ironpython.

Thanks