Unicode C

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.

Unicode C

#include <C_CkPdfW.h>
#include <C_CkJsonObjectW.h>
#include <C_CkCertW.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkPdfW pdf;
    HCkJsonObjectW json;
    HCkCertW cert;

    success = FALSE;

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

    pdf = CkPdfW_Create();

    // Load a PDF to be signed.
    success = CkPdfW_LoadFile(pdf,L"qa_data/pdf/sign_testing_4/hello_signed.pdf");
    if (success == FALSE) {
        wprintf(L"%s\n",CkPdfW_lastErrorText(pdf));
        CkPdfW_Dispose(pdf);
        return;
    }

    // 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.
    json = CkJsonObjectW_Create();

    // In most cases, the signingCertificateV2 and signingTime attributes are required.
    CkJsonObjectW_UpdateInt(json,L"signingCertificateV2",1);
    CkJsonObjectW_UpdateInt(json,L"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"
    CkJsonObjectW_UpdateInt(json,L"page",1);
    CkJsonObjectW_UpdateString(json,L"appearance.y",L"under");

    CkJsonObjectW_UpdateString(json,L"appearance.fontScale",L"10.0");

    CkJsonObjectW_UpdateString(json,L"appearance.text[0]",L"Reason: Agreement Accepted by John");
    CkJsonObjectW_UpdateString(json,L"appearance.text[1]",L"Date: current_dt");

    // Load the signing certificate. (Use your own certificate.)
    cert = CkCertW_Create();
    success = CkCertW_LoadPfxFile(cert,L"qa_data/pfx/myPdfSigningCert.pfx",L"secret");
    if (success == FALSE) {
        wprintf(L"%s\n",CkCertW_lastErrorText(cert));
        CkPdfW_Dispose(pdf);
        CkJsonObjectW_Dispose(json);
        CkCertW_Dispose(cert);
        return;
    }

    // Tell the pdf object to use the certificate for signing.
    success = CkPdfW_SetSigningCert(pdf,cert);
    if (success == FALSE) {
        wprintf(L"%s\n",CkPdfW_lastErrorText(pdf));
        CkPdfW_Dispose(pdf);
        CkJsonObjectW_Dispose(json);
        CkCertW_Dispose(cert);
        return;
    }

    // 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:
    CkPdfW_putUncommonOptions(pdf,L"NO_VERIFY_CERT_SIGNATURES");

    success = CkPdfW_SignPdf(pdf,json,L"qa_output/hello_signed.pdf");
    if (success == FALSE) {
        wprintf(L"%s\n",CkPdfW_lastErrorText(pdf));
        CkPdfW_Dispose(pdf);
        CkJsonObjectW_Dispose(json);
        CkCertW_Dispose(cert);
        return;
    }

    wprintf(L"The PDF has been successfully cryptographically signed.\n");

    // 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)


    CkPdfW_Dispose(pdf);
    CkJsonObjectW_Dispose(json);
    CkCertW_Dispose(cert);

    }