Creating Signed PDF Documents

You can create electronically signed PDF documents. You can even add more than one signature.
For this, what you need is

iTextSharp
an electronic signature (a USB token or a PFX certificate file)
helper DLLs

Using these, you can put more than one signature on a document.
By using signing tools such as SafeNet, you can make your certificate visible.
If you plug more than one USB token into a single computer, the signatures will clash. To get round this, you can try spreading them
across more than one server.

There are 3 types of signature
CAdES: All documents
PAdES: PDFs
XAdES: XML documents