[jira] [Comment Edited] (TIKA-4756) Detecting Signatures in PDFs with AcroForm

[Tilman Hausherr (Jira)]

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https://issues.apache.org/jira/browse/TIKA-4756?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18088278#comment-18088278
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Tilman Hausherr edited comment on TIKA-4756 at 6/11/26 2:15 PM:
----------------------------------------------------------------

The change is still useful for others even if Willy decides to detect 
signatures with local code. The advantage of doing it locally is that you don't 
have to wait for the next tika version 😂


was (Author: tilman):
The change is still useful for others even if Willy decides to detect 
signatures with local code.

> Detecting Signatures in PDFs with AcroForm
> ------------------------------------------
>
>                 Key: TIKA-4756
>                 URL: https://issues.apache.org/jira/browse/TIKA-4756
>             Project: Tika
>          Issue Type: Improvement
>          Components: metadata
>            Reporter: Willy T. Koch
>            Priority: Minor
>              Labels: Signature
>         Attachments: sigflags_sample.pdf, signature.png
>
>
> We see that PDFs that have an Acroform that contains a signture /Sig fields 
> aren't detected by the /meta analysis. It detects the AcroForm with  
> "pdf:hasAcroFormFields": "true", but nothing on the /Sig part. They are 
> created directly in Adobe Acrobat which is also possible in the Free version.
> It would be very useful to also return   "hasSignature": "true" (or some 
> other signature: property) in these kinds of filees, so we can handle it on 
> our end. We use this to exluce PDFs with digital signatures from being 
> reconverted to PDF/A.
>  
> When I run it through the OCRmyPDF, it flags it as digitally signed and 
> exits, which is how I first noticed it.
> _ocrmypdf sigflags_sample.pdf sigflags_sample_ocrmypdf.pdf_
> _DigitalSignatureError: Input PDF has a digital signature. OCR would alter 
> the document,_
> _invalidating the signature._
>  
> I've attached a small sample PDF with AcroForm and Signature to reproduce the 
> issue.
>  
> Willy T. Koch
> Technical Product manager,
> Public 360°
> Norway



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