PDF is an open standard, except when it's not [LWN.net]

PDF is an open standard, except when it's not

Posted Jun 7, 2025 18:15 UTC (Sat) by marcH (subscriber, #57642)
Parent article: The importance of free software to science

> PDF files are based on an open, versioned standard and will be readable into the foreseeable future with all of the formatting details preserved.

Yes and no. There is indeed a standard, which was a gift from Adobe, and we should be grateful.

More recently, Adobe has been adding proprietary extensions to the PDF format and these can only be open using Adobe software. A famous example is XFA forms produced by LifeCycle designer.

Ironically, this was deprecated by Adobe itself. Probably because people don't buy computers anymore. They only have a smartphone and for some reason XFA never worked on smartphones. But Adobe LifeCycle designer is still around and still producing unusable PDFs.

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PDF is an open standard, except when it's not

Posted Jun 7, 2025 18:24 UTC (Sat) by marcH (subscriber, #57642) [Link] (4 responses)

To be more precise: it sounds possible to read static XFA with Adobe software, even on Linux.

Dynamic XFA is the "real deal" https://kbdeveloper.qoppa.com/livecycle-dynamic-xfa-forms/
> There are very few PDF viewers that support XFA Dynamic Forms, one can count them on the fingers of one hand.

Both static and dynamic XFA have been deprecated in PDF 2.0?

(That entire confusion and lack of standardization is the problem)

PDF is an open standard, except when it's not

Posted Jun 9, 2025 5:07 UTC (Mon) by DemiMarie (subscriber, #164188) [Link] (3 responses)

PDF.is can handle XFA just fine.

PDF is an open standard, except when it's not

Posted Jun 9, 2025 14:05 UTC (Mon) by marcH (subscriber, #57642) [Link] (2 responses)

I tried opening a dynamic XFA form on pdf.is and it went much further than everything I tried before, thanks for the recommendation! I can at least see and fill the form, that's great progress. However the form also shows:

> JavaScript has been disabled, the form requires JavaScript to validate properly.
>
> Please enable JavaScript through Preferences under the Edit menu and reopen the form.

The "Validate" and "Clear Form" have no effect.

Maybe it would work better with a higher subscription tiers? But even if it does, we're straying away from "open", "portable" and "reproducible"...

I also tried to convert it to PDF/A and the output still shows "Please Wait..."

I admit dynamic XFA is unlikely to be used by a scientist. But 1. you never know 2. there could be other proprietary extensions.

tl;dr: beware proprietary extensions.

PDF is an open standard, except when it's not

Posted Jun 9, 2025 14:10 UTC (Mon) by DemiMarie (subscriber, #164188) [Link] (1 responses)

Try opening the PDF in Firefox’s or Tor Browser’s built-in PDF viewer. Those might have JavaScript enabled.

PDF is an open standard, except when it's not

Posted Jun 9, 2025 16:18 UTC (Mon) by marcH (subscriber, #57642) [Link]

No difference in Firefox, I'm curious why you expected some?

PDF is an open standard, except when it's not

Posted Jun 7, 2025 18:30 UTC (Sat) by leephillips (subscriber, #100450) [Link] (4 responses)

Implicit in my recommendation is that we should only produce PDFs that adhere to the open standard, avoiding the use of any proprietary extensions. This will be the case as a matter of course when using LaTeX.

PDF is an open standard, except when it's not

Posted Jun 7, 2025 19:34 UTC (Sat) by marcH (subscriber, #57642) [Link] (2 responses)

> Implicit in my recommendation is that we should only produce PDFs that adhere to the open standard, avoiding the use of any proprietary extensions

This should not be implicit. People should not believe that "PDF" automatically means "good". Usually: yes. Always: no. I think the article as it is now gives that wrong impression.

PDF is an open standard, except when it's not

Posted Jun 7, 2025 19:56 UTC (Sat) by leephillips (subscriber, #100450) [Link] (1 responses)

Which free software tools produce PDFs making use of Adobe’s proprietary extensions?

PDF is an open standard, except when it's not

Posted Jun 8, 2025 0:09 UTC (Sun) by marcH (subscriber, #57642) [Link]

No idea, that's totally besides my point.

PDF is an open standard, except when it's not

Posted Jun 8, 2025 2:24 UTC (Sun) by spigot (subscriber, #50709) [Link]

At a previous job we had to save legal documents (e.g. contracts), and the requirement was to use PDF/A, which standardizes a subset of PDF features. It's intended for archival purposes.