C

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.

C

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

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

    success = FALSE;

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

    pdf = CkPdf_Create();

    //  Load a PDF containing an unsigned signature field.
    success = CkPdf_LoadFile(pdf,"qa_data/pdf/unsigned_sig_field/due_diligence.pdf");
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_Dispose(pdf);
        return;
    }

    //  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.
    json = CkJsonObject_Create();

    //  In most cases, the signingCertificateV2 and signingTime attributes are required.
    CkJsonObject_UpdateInt(json,"signingCertificateV2",1);
    CkJsonObject_UpdateInt(json,"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.
    CkJsonObject_UpdateBool(json,"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
    CkJsonObject_UpdateString(json,"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.
    CkJsonObject_UpdateString(json,"appearance.text[0]","Digitally signed by: cert_cn");
    CkJsonObject_UpdateString(json,"appearance.text[1]","current_dt");
    CkJsonObject_UpdateString(json,"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).
    CkJsonObject_UpdateString(json,"appearance.image","green-check-grey-circle");
    CkJsonObject_UpdateString(json,"appearance.imagePlacement","left");

    //  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;
    }

    success = CkPdf_SignPdf(pdf,json,"qa_output/due_diligence_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");

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


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

    }