To insert digital signatures or making other actions to PDF files, SignLib library calls an external library named iTextSharp 4.1.6. iTextSharp 4.1.6 library is licensed under MPL / LGPLv2. The original library is available here: https://www.nuget.org/packages/iTextSharp-LGPL/

SignLib library is based on Bouncy Castle library.

The source code of the original iTextSharp 4.1.6 library with all changes and the Bouncy Castle library and all changes are available here: https://www.signfiles.com/license/SignLibSrc.zip