c# 给pdf添加数字签名的步骤

//新建一个PDF文档对象，再添加一个新页面。
PdfDocument doc = new PdfDocument();
doc.Pages.Add();
//加载一个PDF证书      
PdfCertificate cert = new PdfCertificate(@"C:\Users\Administrator\Desktop\gary.pfx", "e-iceblue");

//添加数字签名
var signature = new PdfSignature(doc, doc.Pages[0], cert, "Requestd1");
//设置数字签名的位置
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 = "Le document est certifie";

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

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

signature.Certificated = false;

signature.ConfigGraphicType = ConfiguerGraphicType.TextSignInformation;

signature.DocumentPermissions = PdfCertificationFlags.ForbidChanges;

//保存文档
doc.SaveToFile("sample.pdf");
//打开文档
System.Diagnostics.Process.Start("sample.pdf");