C# iTextSharp electronic signature

Buyer desires to have an existing C# application modified to allow users to 1) specify a fillable PDF to be electronically signed, 2) capture signature from Topaz signature pad, 3) put captured signature(s) onto fillable PDF in the signature lines, and 4) save the PDF and protect it from future modifications after it has been signed. The PDF could have two or three signatures that need to be captured and put on the document. There are also a few checkboxes on the fillable PDF that the user will need to be able to check or uncheck via the signature pad.