使用ItextSharp将TimeStamp令牌设置为签名

Document document = new Document();
PdfWriter writer = PdfWriter.GetInstance(document, new FileStream("output.pdf", FileMode.Create));
document.Open();

PdfFormField signatureField = PdfFormField.CreateSignature(writer);
signatureField.FieldName = "Signature";
signatureField.SetWidget(new Rectangle(100, 100, 200, 150), PdfAnnotation.HIGHLIGHT_INVERT);

PdfSignatureAppearance appearance = writer.SignatureAppearance;
appearance.SignatureGraphic = Image.GetInstance("timestamp.png");
appearance.SignatureRenderingMode = PdfSignatureAppearance.RenderingMode.GRAPHIC_AND_DESCRIPTION;
appearance.Layer2Text = "TimeStamp: " + DateTime.Now.ToString();

document.Add(signatureField);

document.Close();