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https://issues.apache.org/jira/browse/TIKA-4756?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18088172#comment-18088172
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Tim Allison commented on TIKA-4756:
-----------------------------------
I opened a PR before seeing [~tilman] 's points. If it is easy enough to modify
your work flow with custom code, I think that would be preferable.
I think it would be really, really rare that a user would want to see that
there was an empty signature field.
The obvious corner case to Tilman's solution is if you need to have this info
from PDFs inside msg inside zips, etc. If you're only parsing standalone PDFs,
I think Tilman's approach would be better.
> 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
>
>
> 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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