(C) PDF Sign Under Existing Signature

See more PDF Signatures Examples

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

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#include <C_CkPdf.h>
#include <C_CkJsonObject.h>
#include <C_CkCert.h>

void ChilkatSample(void)
    {
    HCkPdf pdf;
    BOOL success;
    HCkJsonObject json;
    HCkCert cert;

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

    pdf = CkPdf_Create();

    // Load a PDF to be signed.
    success = CkPdf_LoadFile(pdf,"qa_data/pdf/sign_testing_4/hello_signed.pdf");
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_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.)

    

    // Options for signing are specified in JSON.
    json = CkJsonObject_Create();

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

    CkJsonObject_UpdateString(json,"appearance.fontScale","10.0");

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

    // Load the signing certificate. (Use your own certificate.)
    cert = CkCert_Create();
    success = CkCert_LoadPfxFile(cert,"qa_data/pfx/myPdfSigningCert.pfx","secret");
    if (success == FALSE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkCert_Dispose(cert);
        return;
    }

    // Tell the pdf object to use the certificate for signing.
    success = CkPdf_SetSigningCert(pdf,cert);
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkCert_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:
    CkPdf_putUncommonOptions(pdf,"NO_VERIFY_CERT_SIGNATURES");

    success = CkPdf_SignPdf(pdf,json,"qa_output/hello_signed.pdf");
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkCert_Dispose(cert);
        return;
    }

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

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

    


    CkPdf_Dispose(pdf);
    CkJsonObject_Dispose(json);
    CkCert_Dispose(cert);

    }