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Re: PDF reading order and tag order

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From: Duff Johnson
Date: Jun 7, 2017 12:51PM

A couple of things to be said...

> Add braille printers to the lineup that use the order panel, not the tags. At least that was the case a couple of years ago when some of our clients with visitors centers were printing braille visitor guides.

No-one should be under the impression that there's anything about the "order panel" that's truly about accessibility. For the purposes of this conversation it can be boiled down as follows:

- The 'order panel- in Acrobat Professional denotes the sequence in which objects are painted onto the page. This is fundamentally orthogonal to the question of 'reading order-, which is denoted *entirely* by the use of "tagged PDF-. Often, they align to one degree or another. In most cases, there are significant discontinuities.

- Software either uses or does not use 'tagged PDF-

- Software that does not use tagged PDF (such as the Reflow feature in Adobe Reader, for example) has to guess to infer a reading-order. Leaving such accessibility basics up to software heuristics is manifestly NOT what accessibility is all about.

- As a concession to today's world where many AT software don't 'do- tagged PDF, Bevi's right that aligning content order and tag order to the extent possible creates value for users who are saddled with the aforementioned software.

> Talking with a colleague, it's hard for us to know which technologies use which order and there's no central source of information that covers all of the A.T. on the market today. Plus people might be using older A.T. that could be using the order, not the tags.

There's nothing fixed about this. While current-generation AT software may not used tagged PDF, the next version of that software may do so. But not, of course, if people don't ask for it.

> Our recommendation: try to get both to synch up, but if you have to compromise, make the tags accurate and the order can slide a bit. Not too much, but a bit.

Since the 'order panel- can't accommodate discontinuous content... or even a paragraph that spans two pages, compromise is indeed essential.

It's just as important to educate service bureaus and the like to point out to them that if they are getting their 'reading order- from page-content instead of from tags (when present) they are doing their end-users a disservice.

Trying to design a PDF file to accommodate software that does not use PDF accessibility is something one should consider carefully, and preferably, reject. In my view, it makes more sense to insist on software that actually understands accessible PDF files (contact the vendor!!!) rather than invest in the prodigious amounts of labor required to make PDF files sort-of 'work- with manifestly substandard software.

Duff.



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