I want to sign a pdf with one signature with appearance on every page
Here is what I do:
Create the stamper
 PdfStamper st = PdfStamper.CreateSignature(reader, new FileStream(this.outputPDF, FileMode.Create, FileAccess.Write), '\0', null, true);
Get the signature appearance
PdfSignatureAppearance sap = st.SignatureAppearance;
populate the properties
 sap.SetCrypto(...);
 sap.Reason = SomeString;
 sap.Contact = SomeString;
 sap.Location = SomeString;
Each stamper has one appearance. I am able to set only signature appearance. Has anyone done something like that? Do I have to create a List of Stampers or a List of SignatureAppearances?