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PDF Sign Unsigned Signature Field

See more PDF Signatures Examples

Demonstrates how to sign a PDF's unsigned signature field.

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

B4X

Dim success As Boolean = False

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

Dim pdf As ChilkatPdf
pdf.Initialize("pdf")

'  Load a PDF containing an unsigned signature field.
success = pdf.LoadFile("qa_data/pdf/unsigned_sig_field/due_diligence.pdf")
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If


'  A PDF with an unsigned signature field appears in Adobe Acrobat as shown below.
'  (When the mouse pointer is hovered over the field, a tooltip will likely show a message
'  such as "Unsigned signature field (Click to sign)".  
'  This example code will automatically find the unsigned signature field,
'  and signs using your certificate.  It automatically sizes the text to the space alotted
'  for the signature.
'  (image:https://example-code.com/images/unsignedSigField.jpg/endImage)

'  Options for signing are specified in JSON.
Dim json As ChilkatJsonObject
json.Initialize

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

'  We don't specify the page or a specific location because Chilkat will automatically
'  find the unsigned signature field and use its location and size and will scale the
'  signatures visual appearance (text + graphics) to the correct size required to fit.
'  We only need to indicate the desire to fill the unsigned signature field.
json.UpdateBool("appearance.fillUnsignedSignatureField", True)

'  Starting in Chilkat v9.5.0.90, if a PDF contains multiple unsigned signature fields,
'  the field to be signed can be chosen by name:
'  To list unsigned signature fields, see this example: List PDF Unsigned Signature Fields
json.UpdateString("unsignedSignatureField", "doctor_signature")

'  Note: If the PDF document contains multiple unsigned signature fields, Chilkat will 
'  sign the 1st one found. 

'  In this example, the appearance of the digital signature will contain three lines:
'  1) The signing certificate's common name
'  2) The current date/time
'  3) Some arbitrary text.
'  The keyword "cert_cn" is replaced with the Certificate's Subject Common Name.
'  The keyword "current_dt" is replaced with the current date/time.
'  Any number of appearance text lines can be added.
json.UpdateString("appearance.text[0]", "Digitally signed by: cert_cn")
json.UpdateString("appearance.text[1]", "current_dt")
json.UpdateString("appearance.text[2]", "The crazy brown fox jumps over the lazy dog.")

'  This signature will include one of the built-in SVG graphics (green-check-grey-circle).
json.UpdateString("appearance.image", "green-check-grey-circle")
json.UpdateString("appearance.imagePlacement", "left")

'  Load the signing certificate. (Use your own certificate.)
Dim cert As ChilkatCert
cert.Initialize("cert")
success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx", "secret")
If success = False Then
    Log(cert.LastErrorText)
    Return
End If


'  Tell the pdf object to use the certificate for signing.
success = pdf.SetSigningCert(cert)
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If


success = pdf.SignPdf(json, "qa_output/due_diligence_signed.pdf")
If success = False Then
    Log(pdf.LastErrorText)
    Return
End If


Log("The PDF has been successfully cryptographically signed.")

'  The appearance of the signature appears in Adobe Acrobat as shown below.
'  (image:https://example-code.com/images/signature3.jpg/endImage)