One of the new features in Acrobat 8.0 Professional garnering significant comment is redaction. This handy tool allowing users to permanently eliminate text or graphics from a PDF page. Solid, simple idea – what’s not to like?
Thus far, Acrobat 8’s redaction tool has been generally well received in principle, although a few discriminating reviewers have also noted a key concern with the method Adobe chose for redaction in Acrobat 8.0, as we shall see.
Acrobat 8 Professional is the first Adobe software to include a redaction feature for PDF, but it’s not the first. Acting on a request from Adobe, in 1996, Appligent developed and released the first version of Redax, which quickly became the definitive tool for serious redaction work on PDF files. The latest version of Appligent’s Redax works with Acrobat Standard and Professional versions 6, 7 and 8. So you don’t need to upgrade to Acrobat 8 Professional to get PDF redaction.
To help me evaluate Acrobat 8 Pro’s new redaction tool, I wanted to find out more about how people use (or fail to use) the one PDF redaction tool that’s been available for over 10 years. I talked to Mark Gavin, founder and CTO of Appligent, to get his take. I began by asking Mark to explain the basic difference in the way Redax and Acrobat redact PDF. The answer was illuminating.
“There are two primary differences between Adobe’s redaction and Appligent’s redaction,” Gavin says. “Appligent uses an “additive” redaction methodology while Adobe uses a “subtractive” redaction methodology.”
OK, sounds technical… but redaction is redaction, right? Who cares how you zap it? This is where Gavin set me straight.
“Adobe takes an existing document and attempts to remove or “subtract” information,” says Gavin. “Appligent creates a new blank document and then “adds” the non-redacted information into the new document. Thus, the new document has never been touched by the information to be redacted.”
So, why does this matter?
Although Acrobat redacts the way you might intuitively expect (subtraction), this method is flawed. As I saw for myself almost as soon as I started redacting with Acrobat 8 Pro, I managed to “nuke” my original document by carelessly doing something that’s routine for me in other document workflows – a “Save As” operation in which I over-write my original file before I’d even realized what I was doing. I’m not exactly the average user, so this got me thinking.
Someone who makes this mistake while redacting in Acrobat 8 Pro, will be running for the backup tapes – if there are any. Once redacted, that data is GONE. That’s a pretty harsh penalty for a easy fumble with a single keystroke. Redax’s redaction method, by contrast, makes it pretty much impossible to damage the original document.
The problem arises because Acrobat merely offers the user a ‘Save As” opportunity rather than assuming that the redacted file must be, of necessity, a new version of the document… a redacted version. Inattentive users and system crashes are known threats to be engineered around. In principle, no redaction workflow should EVER put the original document at risk.
Gavin went on to explain that Acrobat’s method forces the application (and the user) to locate and remove all of the document metadata with an extra step, even custom metadata that Acrobat knows nothing about. Since Redax creates a new blank document, the only information retained is that specifically requested by the user – the text and metadata they affirmatively chose NOT to redact.
The second major difference between Acrobat and Redax, according to Gavin, is that Redax is designed to redact in a “fail safe” manner where Acrobat is not.
“If for whatever reason the document is not redacted correctly, this must be made very clear to the user that something is wrong,” Gavin says. “One of the techniques Redax employs to ensure fail safe operation is to use transparent zones to identify redaction areas. If any text or graphics remains in the redacted document it can easily be seen by the end user. On the other hand, Acrobat’s redaction zones are completely opaque. Since on occasion the Adobe software will fail to redact all the information correctly, the user won’t be able to easily see that information has been left behind.”
For these reasons, I cannot as yet recommend Acrobat’s redaction, free as it is (with the purchase price of Acrobat 8 Pro), over the fail safe and time-tested Redax.
Originally posted on Duff Johnson’s PDF Perspective blog for acrobatusers.com.
by Duff Johnson