GroupDocs.Signature for .NET - API Reference
GroupDocs.Signature for .NET is an outstanding electronic signature API that allows you to esign PDF and Microsoft Word documents, Excel spreadsheets, PowerPoint presentations, images with various types of signatures - digital certificate, image, stamp, text and hand-written signatures, QR-Code or BarCodes and many more!
The namespace provides classes for signing documents of different formats with stamps, barcodes, QR-codes, text, image, metadata, form field and digital signatures.

The main classes in this namespace are:
The namespace provides classes for working with document representation.
The namespace provides classes to specify additional options when loading, signing, verifying, searching and saving documents.