How to digitally sign a PDF (or other document) in Java?

Question

What libraries can be used to digitally sign documents in Java?

Answer 1

iText is probably the library of the highest quality PDF files that I have seen, both commercial and open source, and it can absolutely be used to sign PDF documents.

• From the documentation .
• A blog entry describing how to do this .

Answer 2

Since PDF has explicit support for digital signatures, the process of signing them is different from what you may have to use for “another document,” as you already indicated .

If you have a document format that does not support digital signature, "embedded", you can transfer it to another format that supports digital signatures, such as S / MIME. Support for BouncyCastle S / MIME is fine.

Answer 3

There is a section on the iText website specifically to address this scenario.