Java 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. Chilkat2 Java

import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.JsonObject;
import com.chilkatsoft.chilkat2.Pdf;

public class ChilkatExample {

    public static void main(String[] args) {
        // 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

        Pdf pdf = new Pdf();
        try {
            pdf.loadFile("qa_data/pdf/invoice_signed.pdf");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("Signatures: " + pdf.getNumSignatures());

        JsonObject json = new JsonObject();
        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.
        JsonObject jsonOut = new JsonObject();
        try {
            pdf.textReplace("check", json, jsonOut);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("check: ok = " + jsonOut.boolOf("ok"));

        // "apply" is refused while PreserveSignatures is true (the default).
        try {
            pdf.textReplace("apply", json, jsonOut);
        } catch (ChilkatException e) {
            System.out.println("apply refused: " + e.getLastErrorText());
        }

        // Allowing the signature to be broken:
        pdf.setPreserveSignatures(false);
        try {
            pdf.textReplace("apply", json, jsonOut);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("applied: " + jsonOut.boolOf("applied"));

        // 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.
        try {
            pdf.writeFile("qa_output/invoice_reissued_broken_signature.pdf");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("Signatures after writing: " + pdf.getNumSignatures());
        JsonObject sigInfo = new JsonObject();
        boolean validated;
        try {
            pdf.verifySignature(0, sigInfo);
            validated = true;
        } catch (ChilkatException e) {
            validated = false;
        }
        System.out.println("Signature 0 verifies: " + validated);

        // 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
    }
}