AutoIt 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. AutoIt

Local $bSuccess = 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

$oPdf = ObjCreate("Chilkat.Pdf")
$bSuccess = $oPdf.LoadFile("qa_data/pdf/invoice_signed.pdf")
If ($bSuccess = False) Then
    ConsoleWrite($oPdf.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite("Signatures: " & $oPdf.NumSignatures & @CRLF)

$oJson = ObjCreate("Chilkat.JsonObject")
$oJson.UpdateString("labels[0].label","Invoice Number:")
$oJson.UpdateString("labels[0].value","INV-2026-0500")

;  "check" reads only, so it works on a signed PDF.
$oJsonOut = ObjCreate("Chilkat.JsonObject")
$bSuccess = $oPdf.TextReplace("check",$oJson,$oJsonOut)
If ($bSuccess = False) Then
    ConsoleWrite($oPdf.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite("check: ok = " & $oJsonOut.BoolOf("ok") & @CRLF)

;  "apply" is refused while PreserveSignatures is true (the default).
$bSuccess = $oPdf.TextReplace("apply",$oJson,$oJsonOut)
If ($bSuccess = False) Then
    ConsoleWrite("apply refused: " & $oPdf.LastErrorText & @CRLF)
EndIf

;  Allowing the signature to be broken:
$oPdf.PreserveSignatures = False
$bSuccess = $oPdf.TextReplace("apply",$oJson,$oJsonOut)
If ($bSuccess = False) Then
    ConsoleWrite($oPdf.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite("applied: " & $oJsonOut.BoolOf("applied") & @CRLF)

;  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.
$bSuccess = $oPdf.WriteFile("qa_output/invoice_reissued_broken_signature.pdf")
If ($bSuccess = False) Then
    ConsoleWrite($oPdf.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite("Signatures after writing: " & $oPdf.NumSignatures & @CRLF)
$oSigInfo = ObjCreate("Chilkat.JsonObject")
Local $bValidated = $oPdf.VerifySignature(0,$oSigInfo)
ConsoleWrite("Signature 0 verifies: " & $bValidated & @CRLF)

;  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