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Re: Redacted Text (was Strike-through Text)

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From: Duff Johnson
Date: Apr 2, 2013 1:30PM

Gary,

First: Word and HTML. While some plugins are available (or so I've heard), successful redaction is rare in these formats; they just aren't well-suited to content removal. PDF, wherein each page essentially consists of lots of little drawings, is ideal in the vast majority of cases that don't involve a grease-pen or an Exacto knife (the traditional tools of redaction).

It's true you can redact PDF documents using Acrobat (and it's not the only such tool). There are, however, several things a responsible redactor needs to know that aren't altogether obvious..

1) Acrobat's redaction isn't comprehensive. While it removes content from the page it leaves the tags as-is. Accordingly, the fact of paragraphs, images, lists, etc. (don't forget the alt. text!!) remain in the tags tree even though they're been removed from the document. There's nothing left for AT to voice / zoom on / whatever, but the document structure is *not* redacted along with the content.

This might be fine for many applications, but national security agencies and other professionally paranoid types may feel otherwise. I also loathe Acrobat's selection model for redaction purposes, but I digress... that's not a gripe for this list.

2) The problem with Acrobat's redaction method from the accessibility point of view is that Acrobat by default leaves no indication that a redaction has occurred. A sighted user can see (in most cases) that a chunk of content is missing from the page, but this information is not available to AT users.

Whether redactions are invisible or visible, however, once you do redact using Acrobat you now need to ensure that your redactions (and the remaining content) are still tagged correctly. What if you redacted two items from a list? You'd need to remove those LI tags that used to include the redacted content, right? And so on.

I was thinking of writing a blog-post on this but I may as well spill it now….


How to redact PDF files in Acrobat while ensuring conformance with PDF/UA and WCAG 2.0:

1. Alter Acrobat's "Redaction Properties" to give the redacted area a Fill Color. Black seems to be the general favorite; I'm partial to a semi-transparent gray.

2. Go ahead and Mark areas or content for redaction, then Apply and Save. Now you have a nice PDF with blocks showing your redactions. So far, so good… you have a visual indication that a redaction has taken place.

(I'll stop here to say that if your intention is to create *invisible* redactions - i.e. - that the fact of a redaction is *not* apparent to any reader, then leave your Acrobat redaction defaults alone (set to "transparent). You'll still need to do step 4, though).

4. Clean up your tags; remove the tags that once enclosed content now redacted. If you redacted text within a tag you'll need to split that tag into two (enclosing the content "before" and "after" the redaction to allow the redaction mark's tag to go into correct logical reading order.

5. Tag the redaction mark (a "Figure" tag is appropriate in today's PDF) with alt. text: "Redacted content" or other, as you prefer. Depending on how the document was created and the extent of your redactions you may prefer to simply re-tag the whole PDF. This has the advantage that the auto-tagger will find all the redaction blocks and tag them as "Figure" for you (or, it should).

I hope this helps.

Duff Johnson

Independent Consultant
ISO 32000 Intl. Project Co-Leader, US Chairman
ISO 14289 US Chairman
PDF Association Vice-Chairman

p +1.617.283.4226
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On Apr 2, 2013, at 1:57 PM, Andrew Kirkpatrick < <EMAIL REMOVED> > wrote:

> Gary,
> In acrobat you can redact text. In doing so, the text that is redacted is removed from the tag tree and content tree for the document, so when it is redacted it is gone.
>
> Thanks,
> AWK
>
> Andrew Kirkpatrick
> Group Product Manager, Accessibility
> Adobe Systems
>
> <EMAIL REMOVED>
> http://twitter.com/awkawk
> http://blogs.adobe.com/accessibility
>
>
>