How to add visible digital signature to PDF in C#

Digital signature is one of the ways of document encryption, which is widely used in work. This article provides how to use C# language to add digital signature to PDF documents for reference.

Tools used: Free Spire.PDF for .NET

Note: Before code operation, you need to add the reference DLL file to the project and add it to the namespace at the same time

(This article is reproduced from http://www.cnblogs.com/Yesi/p/6665453.html)

//Create a new PDF document object and add a new page.
PdfDocument doc = new PdfDocument();
doc.Pages.Add();
//Load a PDF certificate           
PdfCertificate cert = new PdfCertificate(@"C:\Users\Administrator\Desktop\gary.pfx", "e-iceblue");

//add digital signature
var signature = new PdfSignature(doc, doc.Pages[0], cert, "Requestd1");
//Set the location of the digital signature
signature.Bounds = new RectangleF(new PointF(280, 600), new SizeF(260, 90));

signature.IsTag = true;

signature.DigitalSignerLable = "Digitally signed by";
signature.DigitalSigner = "Gary for Test";

signature.DistinguishedName = "DN:";
signature.LocationInfoLabel = "Location:";
signature.LocationInfo = "London";

signature.ReasonLabel = "Reason: ";
signature.Reason = "The document is certified";

signature.DateLabel = "Date: ";
signature.Date = DateTime.Now;

signature.ContactInfoLabel = "Contact: ";
signature.ContactInfo = "123456789";

signature.Certificated = false;

signature.ConfigGraphicType = ConfiguerGraphicType.TextSignInformation;

signature.DocumentPermissions = PdfCertificationFlags.ForbidChanges;

// save the document
doc.SaveToFile("sample.pdf");
// open the document
System.Diagnostics.Process.Start("sample.pdf");

 Example of effect:

(End of this article)