Change is constant, and it is natural to want to develop improved versions of products. The thing that horrifies me is when developers launch a new product (or version) which unwittingly or otherwise  misses out on feature and capabilities of the earlier version that users need and depend on.

I've described this in one of my blogs. See The "Do No Harm" principle which in essence states that the behavior of the new model/version must be a superset of the earlier behavior.

This is a principle that even major players who should know better like Microsoft, for one, pay insufficient attention to -- being the main reason why I've reverted to Internet Explorer 6 after finding the configurability of the IE7 user interface too limiting, and why I'm sticking with Windows XP preferring it over the stupid user interface and irksome UAC behavior of Windows Vista.

Adobe Acrobat 9 was made available on 25 June 2008, see the press release here. I installed Adobe Reader 9 soon after that, went to switch on this feature -- essential to me, at least -- and was quite shocked to discover that it is missing.

Just to be on the safe side, I've had two independent sources confirm my findings, and now I'm 99.9 percent sure that Adobe Reader 9 has violated the Do No Harm principle. By the way, I'm quite prepared to apologize profusely if I'm proved wrong.

For many users of Adobe Reader the feature concerned may be of little import, but for a power user like me who reads dozens of PDF documents every week it's quite a bitter blow.

What, then, is the missing feature that this old grump considers so important and misses so much in Adobe Reader 9? Please read on to find out.