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Classic ASP

PDF Sign Under Existing Signature

See more PDF Signatures Examples

This example explains how sign a previously-signed PDF and place the signature appearance below the existing signature.

Note: This example requires Chilkat v9.5.0.85 or greater.

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Classic ASP 
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<%
success = 0

'  This example requires the Chilkat API to have been previously unlocked.
'  See Global Unlock Sample for sample code.

set pdf = Server.CreateObject("Chilkat.Pdf")

'  Load a PDF to be signed.
success = pdf.LoadFile("qa_data/pdf/sign_testing_4/hello_signed.pdf")
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( pdf.LastErrorText) & "</pre>"
    Response.End
End If

'  The PDF we'll be signing already has a signature added in Adobe Acrobat DC.
'  It looks like this:
'  (Notice the Adobe background logo, which is commonly what you'll see when a signature
'  is created by Adobe Acrobat.  Chilkat (obviously) does not create signatures using the Adobe
'  logo because it would be a copyright violation.)

'  image

'  Options for signing are specified in JSON.
set json = Server.CreateObject("Chilkat.JsonObject")

'  In most cases, the signingCertificateV2 and signingTime attributes are required.
success = json.UpdateInt("signingCertificateV2",1)
success = json.UpdateInt("signingTime",1)

'  To put our new signature underneath the existing signature, we have to specify the page
'  where the existing signature is found, and then we can specify "under" for the "appearance.y"
success = json.UpdateInt("page",1)
success = json.UpdateString("appearance.y","under")

success = json.UpdateString("appearance.fontScale","10.0")

success = json.UpdateString("appearance.text[0]","Reason: Agreement Accepted by John")
success = json.UpdateString("appearance.text[1]","Date: current_dt")

'  Load the signing certificate. (Use your own certificate.)
set cert = Server.CreateObject("Chilkat.Cert")
success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret")
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( cert.LastErrorText) & "</pre>"
    Response.End
End If

'  Tell the pdf object to use the certificate for signing.
success = pdf.SetSigningCert(cert)
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( pdf.LastErrorText) & "</pre>"
    Response.End
End If

'  Note: When adding an additional signature to a PDF, the existing signatures
'  are validated, and this includes validating the certificates previously used to 
'  create the existing signatures.  (A signature typically embeds the signing certs.)
'  In some cases, the certificates and/or certs in the chain of authentication for 
'  existing signatures are not present, and are not available on the current system.
'  In this case, you can skip the validation by setting this keyword in UncommonOptions:
pdf.UncommonOptions = "NO_VERIFY_CERT_SIGNATURES"

success = pdf.SignPdf(json,"qa_output/hello_signed.pdf")
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( pdf.LastErrorText) & "</pre>"
    Response.End
End If

Response.Write "<pre>" & Server.HTMLEncode( "The PDF has been successfully cryptographically signed.") & "</pre>"

'  Here's a screenshot of the 2nd signature positioned under the 1st in Adobe Acrobat:

'  image

%>
</body>
</html>