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Posted to dev@tika.apache.org by "Tilman Hausherr (Jira)" <ji...@apache.org> on 2026/07/15 08:24:00 UTC
[jira] [Resolved] (TIKA-4756) Detecting Signatures in PDFs with AcroForm
[ https://issues.apache.org/jira/browse/TIKA-4756?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Tilman Hausherr resolved TIKA-4756.
-----------------------------------
Fix Version/s: 4.0.0
3.3.2
Resolution: Fixed
> 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
> Fix For: 4.0.0, 3.3.2
>
> Attachments: image-2026-06-11-18-05-01-275.png, image-2026-06-25-14-24-14-895.png, image-2026-06-25-14-25-42-316.png, 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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