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Digital signatures in C# .NET

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PDF documents often require signatures for authentication purposes, and the use of electronic and digital signatures in PDFs has become increasingly common in recent years. Signatures in PDFs enable individuals and organizations to sign documents electronically, eliminating the need for physical signatures and making it more efficient to conduct business. In this context, signatures in PDFs can provide security, authenticity, and integrity to documents and help streamline the document-signing process.

Nutrient .NET SDK (formerly GdPicture.NET) provides the means to create and modify signature fields. The full range of specialized methods enables you to sign a document with text, an image, or a combination of both. You can also get the details of a signature in a signed PDF document.

For long-term validation workflows, the PDF signing engine supports PAdES-compatible signatures, document timestamp signatures, and LTV signatures with embedded validation material. It also supports ECDSA certificates and PKCS#11-backed signing with hardware security modules, USB tokens, and smartcards.

Nutrient .NET SDK no longer creates new SHA-1 signatures. Existing SHA-1 signatures can still be verified.

Key capabilities

  • Sign with a digital signature — Add and customize digital signatures
  • Different certificate sources — Add certificates from multiple sources
  • Get signature details — Get all signature details from signed PDF documents
  • Add signature fields — Add signature fields and get their properties
  • Multi-signature support — Handle documents with multiple signatures and fill multiple signature fields
  • Long-term validation — Create PAdES-compatible, timestamped, and LTV signatures
  • Hardware-backed signing — Sign with PKCS#11 devices such as HSMs, USB tokens, and smartcards

Guides for PDF signatures

Digital signatures
How to sign with a digital signature

Certify a document
How to add certificates to a PDF document

Add signature fields
How to add signature fields

Fill signature fields
How to fill a signature field

Get signature field properties
How to get a signature field’s properties