How to programmatically digital sign PDF document?

I need to digitally sign PDF documents from Java or C#. I've found iText, is it a good solution? are there any开发者_如何学Python others?

I've tried iText once and it was quite easy to implement in a C# solution. I have not tried other solutions. Esp. I could not find any proper free (no-cost) solutions.

See PDFBox at apache, used in conjunction with BouncyCastle it will do what you require.