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Signature placeholder kb size limit

We are inserting a signature placeholder in a PDF File with Aspose.PDF

FormEditor editor = new FormEditor(doc);
editor.AddField(FieldType.Signature, "signature_1", 1, 1, 1, 200, 70);

The placeholder is shown in Adobe and I can insert a signature with Acrobat => ok

The problem is, that another signing software inserts or adds the signature in the placeholder programmatically (postprocessing). They are using iText as library and the size of the signatures to be inserted are around 30kb (data). If they want to insert it, there is an iText error “Not enough space”.

PdfSigner.SignDeferred(signer.GetDocument(), $"{SignatureFieldName}", outputDocument, aisSignatureContainer);

It seems that there is a limit of around 3kb size? Can this limit be extended with Aspoe.PDF? How?

iText: you must provide the estimated signature size when creating a placeholder

signer.SignExternalContainer(preSigningContainer, EstimatedSignatureSize);


At the moment, there is no such property or mechanism in the API to specify the signature size. Furthermore, we need to further investigate this case as well. Please share a sample PDF (generate using Aspose.PDF) and sample code snippet you used to generate it. We will further investigate the scenario and share our feedback with you accordingly.

Here a testfile

nowhow-sig.pdf (72.5 KB)


Please also share the code snippet that you are using to add the signature field in the PDF. It would help us in investigating the issue accordingly.

Document doc = new Document(dataDir + "nowhow.pdf");
TextFragmentAbsorber absorber = new TextFragmentAbsorber("U-Links");
TextFragmentCollection textFragmentCollection = absorber.TextFragments;

// Create Formeditor
FormEditor editor = new FormEditor(doc);

foreach (TextFragment frag in textFragmentCollection) {
    editor.AddField(FieldType.Signature, "signature_1", frag.Page.Number, (float) frag.Position.XIndent, (float)frag.Position.YIndent, (float) frag.Position.XIndent + 200, (float) frag.Position.YIndent + 70);

editor.Save(dataDir + "AddSignatureFields_1_out.pdf");


An investigation ticket as PDFNET-51716 has been logged in our issue tracking system to further analyze this feature. We will look into ticket details and keep you posted with the status of its rectification. Please be patient and spare us some time.

We are sorry for the inconvenience.

Hi Ali
The Investigation ticket PDFNET-51716 is still in state “Open” - What do you mean by “Please be patient and spare us some time” - What time-frame do you expect? This month, this year, next 5 years, …

We do need to create signature placeholder with size > 3kb
=> or we have to check other possibilities…



The ticket has been logged recently under free support model where issues are resolved on first come first serve basis. The investigation and ticket resolution time depends upon the number of issues logged prior to it as well as nature and complexity of the scenario. Nevertheless, we have recorded your concerns and will surely consider them during ticket investigation. We will let you know once we have more updates.

We apologize for the inconenience.