(C) PDF Signature Page Location

See more PDF Signatures Examples

This example demonstrates how to specify the location of a PDF signature on a page.

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;
    HCkPdf pdf2;

    // 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.
    // The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
    success = CkPdf_LoadFile(pdf,"qa_data/pdf/hello.pdf");
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_Dispose(pdf);
        return;
    }

    // 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);

    // When cryptographically signing a PDF, the signature's appearance can be placed on a specific
    // page in the PDF document, and at a specified location on the page.
    // The 1st page of the PDF document is page number 1 (we don't use 0-based numbering for PDF page numbers).
    // The PDF object has a NumPages property, so we can use it to sign on the last page of the PDF.
    CkJsonObject_UpdateInt(json,"page",CkPdf_getNumPages(pdf));

    // appearance.y and appearance.x JSON properties control the x,y location of the signature.
    // The "appearance.y" can be "top" or "bottom".
    // The "appearance.x" can be "left", "middle", or "right".
    // It is also possible to specify exact PDF location in user space coordinates, which is discussed below.
    CkJsonObject_UpdateString(json,"appearance.y","bottom");
    CkJsonObject_UpdateString(json,"appearance.x","middle");

    // In this example, the fontScale (in combination with the number of appearance text lines and the length of the longest text line),
    // automatically determine the width/height of the signature text box. Any included graphic (JPG image or built-in SVG) is automatically
    // scaled to fit. It is alternatively possible to specify the desired width/height of the signature rectangle.  In that case
    // you would NOT specify a fontScale because Chilkat would automatically chose a font scale to fit the text to the desired rectangle.
    // This example demonstrates how to specify the exact width/height of the PDF signature text box.
    CkJsonObject_UpdateString(json,"appearance.fontScale","9.0");

    CkJsonObject_UpdateString(json,"appearance.text[0]","Digitally signed by: cert_cn");
    CkJsonObject_UpdateString(json,"appearance.text[1]","current_dt");
    CkJsonObject_UpdateString(json,"appearance.image","document-accepted");
    CkJsonObject_UpdateString(json,"appearance.imagePlacement","left");
    CkJsonObject_UpdateString(json,"appearance.imageOpacity","100");

    // Load the signing certificate. (Use your own certificate.)
    cert = CkCert_Create();
    success = CkCert_LoadPfxFile(cert,"qa_data/pfx/myPdfSigningCert.pfx","pfx_password");
    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/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");

    // The appearance of the signature appears in Adobe Acrobat as shown here:

    // ----------------------------------------------------------------------------------------------------
    // *** Scroll down for information about specifying the PDF signature x,y location in user space coordinates.
    // ----------------------------------------------------------------------------------------------------

    

    // The x,y coordinates of a PDF page are in "user space", called "points", and there are 72 pointes per inch.
    // A PDF page (8.5" x 11") is 612 points wide and 792 points high.
    // The bottom left is at 0,0.    The top right is at 612,792.
    // 
    // To specify the location of a signature rectangle, the "appearance.y" is the y coordinate of the top of the signature rectangle,
    // and the "appearance.x" is the x coordinate of the left of the signature rectangle.
    // Therefore, to position the signature rectangle at the exact top/left of the page, we do this:

    CkJsonObject_UpdateString(json,"appearance.y","792");
    CkJsonObject_UpdateString(json,"appearance.x","0");

    CkJsonObject_UpdateString(json,"appearance.text[0]","Digitally signed again by: cert_cn");
    CkJsonObject_UpdateString(json,"appearance.text[1]","current_dt");
    CkJsonObject_UpdateString(json,"appearance.image","document-accepted");
    CkJsonObject_UpdateString(json,"appearance.imagePlacement","right");

    pdf2 = CkPdf_Create();
    success = CkPdf_LoadFile(pdf2,"qa_output/hello_signed.pdf");
    success = CkPdf_SetSigningCert(pdf2,cert);

    success = CkPdf_SignPdf(pdf2,json,"qa_output/hello_signed2.pdf");
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf2));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkCert_Dispose(cert);
        CkPdf_Dispose(pdf2);
        return;
    }

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

    // Here we have the PDF with the signature just added at the exact top/left.
    


    CkPdf_Dispose(pdf);
    CkJsonObject_Dispose(json);
    CkCert_Dispose(cert);
    CkPdf_Dispose(pdf2);

    }