Visual FoxPro

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.

Visual FoxPro

LOCAL lnSuccess
LOCAL loPdf
LOCAL loJson
LOCAL loCert

lnSuccess = 0

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

loPdf = CreateObject('Chilkat.Pdf')

*  Load a PDF to be signed.
lnSuccess = loPdf.LoadFile("qa_data/pdf/sign_testing_4/hello_signed.pdf")
IF (lnSuccess = 0) THEN
    ? loPdf.LastErrorText
    RELEASE loPdf
    CANCEL
ENDIF

*  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:https://example-code.com/images/signed_once_with_adobe_acrobat.jpg/endImage)

*  Options for signing are specified in JSON.
loJson = CreateObject('Chilkat.JsonObject')

*  In most cases, the signingCertificateV2 and signingTime attributes are required.
loJson.UpdateInt("signingCertificateV2",1)
loJson.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"
loJson.UpdateInt("page",1)
loJson.UpdateString("appearance.y","under")

loJson.UpdateString("appearance.fontScale","10.0")

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

*  Load the signing certificate. (Use your own certificate.)
loCert = CreateObject('Chilkat.Cert')
lnSuccess = loCert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","secret")
IF (lnSuccess = 0) THEN
    ? loCert.LastErrorText
    RELEASE loPdf
    RELEASE loJson
    RELEASE loCert
    CANCEL
ENDIF

*  Tell the pdf object to use the certificate for signing.
lnSuccess = loPdf.SetSigningCert(loCert)
IF (lnSuccess = 0) THEN
    ? loPdf.LastErrorText
    RELEASE loPdf
    RELEASE loJson
    RELEASE loCert
    CANCEL
ENDIF

*  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:
loPdf.UncommonOptions = "NO_VERIFY_CERT_SIGNATURES"

lnSuccess = loPdf.SignPdf(loJson,"qa_output/hello_signed.pdf")
IF (lnSuccess = 0) THEN
    ? loPdf.LastErrorText
    RELEASE loPdf
    RELEASE loJson
    RELEASE loCert
    CANCEL
ENDIF

? "The PDF has been successfully cryptographically signed."

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

*  (image:https://example-code.com/images/signed_under_existing_signature.jpg/endImage)

RELEASE loPdf
RELEASE loJson
RELEASE loCert