CoSign API: How can I enable Multi-Page signing through the C# SAPI?

Question

I need the ability to take a multiple page PDF and apply the same signature on each page. Is that capability exposed through SAPI? The number of pages in my document will vary and I would prefer to do this automatically without having to ask the end user how many pages are in the document.

Answer 1

There's no feature like Multi-Page signing in CoSign SAPI , but there are several ways to get the number of pages in a PDF file (you can find some useful suggestions in this SO q ) and then it would be easy for you to implement the signing.

But why do you need the Multi-Page signing ability? If, for example, it because you want to make sure that no one added pages to a contract after it was signed, then one digital signature would be enough. After all, one of the purposes of digital signature is to ensure file integrity.

If however you still prefer to sign all of the document pages, I strongly recommend to sign each page with an electronic signature and only one page (usually the last) with a digital signature.

Otherwise, the signed file will be much bigger and the validation process for the many digital signatures will take a lot longer.