public class DocX : Xceed.Document.NET.Document 

// Add the SignatureLine to the document.

mySignatureLine = document.AddSignatureLine();



// Insert the SignatureLine in a document's paragraph.

myParagraph.AppendSignatureLine( mySignatureLine );



// Create a digital certificate in order to sign the document, by using a pfx file and its password.

var certificate = DigitalCertificate.Create( "CustomCertificate.pfx", "xceed" );



// Create SignOptions for the SignatureLine.

// Use the SignatureLineId to match the SignatureLine id and set the image used to sign the SignatureLine.

var signOptions = new SignOptions()

{

  SignatureLineId = mySignatureLine.Id,

  SignatureLineImage = "MarkStoneSignature.png",

  Comments = "This document is now signed by Mark Stone."

};   



// Sign the document with the certificate and the SignOptions, related to the SignatureLine.

DocX.Sign( "DocumentToSign.docx", "SignedDocument.docx", certificate, signOptions );