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Re: PDF reading order and tag order

for

From: Duff Johnson
Date: Jun 12, 2017 7:56AM

Hi Alastair,

> On this bit:
>> 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.
>
> That came up in a discussion about WCAG 2.1 where we are looking at
> increasing the resize-content aspect:
> https://github.com/w3c/wcag21/issues/77#issuecomment-306385027
>
> Are there techniques for defining (or at least controlling) the order in
> which a PDF document is reflowed?

The first thing to say (boring and repetitive as it may be) is this: software that uses tagged PDF does not have *any* ambiguity about ordering, for reflow or any other purpose. This is why support for tagged PDF is *critical* to accessibility. Software that does *not* support tagged PDF is not AT software with respect to PDF files. Period.

Now... that doesn't stop (a) vendors from selling such software, or (b) end-users confusing such software with that which does support tagged PDF.

So... returning to your question...

If we're talking about strategies for dealing with software that does *not* use tagged PDF, then, yes, the Order panel is useful. Use at your peril however, as the process of re-ordering page-content in PDF is fraught with peril, including the dreaded 'z-order error- in which stuff just seems to.... disappear.

Unfortunately, the junky old 'Touch Up Reading Order Tool- in Acrobat Professional edits *both* tags *and* content order at the same time, with no options to do otherwise and no warning of the problems that can result.

Duff.