C++ Requires Chilkat v11.7.0+

Replace Text in a Signed PDF (PreserveSignatures)

See more PDF Text Replacement Examples

Applying a text replacement rewrites the page content, which invalidates any digital signature on the PDF. While the PreserveSignatures property is true (the default), "apply" is refused on a signed PDF; "check" only reads and is always allowed. Setting PreserveSignatures to false allows the replacement; the signature field stays in the written PDF but no longer verifies, so the document should be signed again afterwards if a signature is wanted. C++

#include <CkPdf.h>
#include <CkJsonObject.h>

void ChilkatSample(void)
    {
    bool success = false;

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

    //  The PDF used in this example is available at invoice_signed.pdf

    CkPdf pdf;
    success = pdf.LoadFile("qa_data/pdf/invoice_signed.pdf");
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Signatures: " << pdf.get_NumSignatures() << "\r\n";

    CkJsonObject json;
    json.UpdateString("labels[0].label","Invoice Number:");
    json.UpdateString("labels[0].value","INV-2026-0500");

    //  "check" reads only, so it works on a signed PDF.
    CkJsonObject jsonOut;
    success = pdf.TextReplace("check",json,jsonOut);
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "check: ok = " << jsonOut.BoolOf("ok") << "\r\n";

    //  "apply" is refused while PreserveSignatures is true (the default).
    success = pdf.TextReplace("apply",json,jsonOut);
    if (success == false) {
        std::cout << "apply refused: " << pdf.lastErrorText() << "\r\n";
    }

    //  Allowing the signature to be broken:
    pdf.put_PreserveSignatures(false);
    success = pdf.TextReplace("apply",json,jsonOut);
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "applied: " << jsonOut.BoolOf("applied") << "\r\n";

    //  The written PDF is a full rewrite with the replacement.  The signature field is still in the document,
    //  but the bytes it signed are gone, so it no longer verifies.
    success = pdf.WriteFile("qa_output/invoice_reissued_broken_signature.pdf");
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Signatures after writing: " << pdf.get_NumSignatures() << "\r\n";
    CkJsonObject sigInfo;
    bool validated = pdf.VerifySignature(0,sigInfo);
    std::cout << "Signature 0 verifies: " << validated << "\r\n";

    //  Sample output:

    //  Signatures: 1
    //  check: ok = true
    //  apply refused: ChilkatLog:
    //    TextReplace:
    //      DllDate: Nov  7 2026
    //      ChilkatVersion: 11.7.0
    //      UnlockPrefix: CHLKAT
    //      UnlockStatus: 2
    //      Architecture: Little Endian; 64-bit
    //      Language: Visual C++ 11.0 / x64
    //      VerboseLogging: 0
    //      replaceTextOp:
    //        op: apply
    //        The PDF is signed: replacing text rewrites the content and invalidates the signatures (set PreserveSignatures = false to allow it).
    //      --replaceTextOp
    //      Failed.
    //    --TextReplace
    //  --ChilkatLog
    //  
    //  applied: true
    //  Signatures after writing: 1
    //  Signature 0 verifies: false
    }