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Re: PDF U/A alternate description for links

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From: Steve Green
Date: Feb 14, 2023 3:45PM

It's certainly an annoying failure because it happens with every link when you create a PDF from Word, regardless of whether you use the Save As PDF option or PDFMaker.



It's worth nothing that the error message does not relate to the Link tag (which contains the link text but not the URL). It relates to the link annotation, which is the clickable area that is associated with the URL – this is not part of the Tags tree, but you can see it in the Content panel.



The Link-OBJR tag creates a relationship between the Link tag and the link annotation and is created automatically during the Word-to-PDF export process. However, not all applications create this relationship and you have to create it manually if you add links in Acrobat.



PDF/UA does not provide a rationale for this requirement, and I can only imagine that there might be some PDF reader applications that do not recognise the relationship that the Link-OBJR tag creates. That said, I have never seen any adverse effect with any PDF reader or assistive technology I have tested with.



I have done some tests with PAC 2021 and the Commonlook PDF Validator, which is much more thorough.



PAC 2021

* Before you apply any fixes it reports failures of "Alternative description missing for an annotation".
* If you add either Alternate Text or the Contents attribute, the error clears.



Commonlook PDF Validator

* Before you apply any fixes it reports failures of "Parent tag of Link annotation doesn't define the Alt attribute” and “Link Annotation doesn't define the Contents attribute”.
* If you add Alternate Text it doesn't report a failure, but it reports a warning of “Link Annotation doesn't define the Contents attribute”.
* If you add the Contents attribute it doesn't report a failure, but it reports a warning of “Parent tag of Link annotation doesn't define the Alt attribute”.

Steve Green
Managing Director
Test Partners Ltd