GIRAFFE6044  I too upgraded with the Adobe Updater without any problems.  
(Version 9.2)

OZEAN  I used Adobe Updater and it worked without any problems. This is in 10.6.1 set to English on a MacBook Pro 2,2.

Also, saving as Adobe PDF finally seems to work. (I never got it to work reliably after updating to 10.6 where there is no Adobe PDF printer anymore. Now we have the Print > PDF > Save as Adobe PDF function, which had big problems - hopefully my impression that those are fixed now is correct!)  
(Version 9.2)

SANCHAI  Adobe Acrobat Pro 9.2 update fail to upgrade 9.1.3 to 9.2 properly. Same failure as mentioned above.

The error dialog read "Update failed. The patch has failed because the application has been modified since it was originally installed (for example, plug-ins may have been disabled). Please go to the Adobe support website for more information regarding how to re-enable disabled components prior to installing the patch. Or, you can install and reinstall the application, and then reinstall the patch."

Adobe Reader update to 9.2 run fine. I have seen this failure in many places around the net. Caome on Adobe here you go again. New update that work please!  
(Version 9.2)

FILCHESCAT  Same here - error message about having modified the Acrobat Pro 9.1.x file and messing around with plug-ins. NOT. Sounds like a bad update app. I downloaded a similar update directly from Adobe's site - same results. Did a lot of un-installing / re-installing with the same results. Come on Adobe.  
(Version 9.2)

ERIC WOEHLER  Forgot to mention - running Vanilla install of CS4 - no plugins removed, no language files removed, no modifications from original CS4 installation other than Adobe updates to 9.1.3!!!

Just tried the updater on a second machine [mirror door G4 desktop) (also unmodified CS4 install) and failed to upgrade: ".. application modified, plugins disabled.." yada yada yada. Negative Adobe - CS4 DVD install and fails to upgrade...

is anyone from Adobe reading this?  
(Version 9.2)

MACLOVER1.1  PAst few updaters I got the seemingly common error message (unable to isntall.. change plugins.. blah blah). It tried everything: reinstalling, logging form a different user account etc.. no it will not update... it scares me for my setup mostly.. because seriously I hardly ever use Acrobat... but what is this error that so may seem to encounter and that is so "mysterious". ADOBE wake up... you are annoying us. Can't it be more precise.. error, like what has supposedly changed form my original install.. when I have just reinstalled like 2mn prior ???! Oh I get it my clock has changed its numbers lol  
(Version 9.1.3)

AWADO  I've been using (or should I say 'trying'?) this app for several years now since version 7. Version 7 was the only one, that seemed to be stable. 8 (updates incl.) crashed very often and sometimes even forced me to reboot. Considering the price this is very frustrating. The demo of version 9 is not much better. It crashes upon quit. (Regardless of any activated fonts or extensions!)  
(Version 9.1.3)

SERGESOUSZERO  Tried to download the trial version... woops ! None available for Mac OS. Reading the comments below makes me think that I'm not missing anything after all.   
(Version 9.1)

NIKO0929  I've downloaded Acrobat Pro 9.0 for mac several times now, and none works more than 1 day. It worked fine the first day I installed the program, but crashes every time I open a pdf file. It won't stay open more than a minute. Does anyone know how I can fix it. It is very frustrating that I can not even finish reading articles.  
(Version 9.1)

ERIC WOEHLER  Just tried to run updater after running the "Repair Acrobat Installation" option under the Help menu in Acrobat. Ran the repair ok, 'repaired' the Acrobat printer (which had been working just fine, thank you for asking), then tried the updater. Same old message, plugins removed, app modified, etc etc

So - it looks like I have to reinstall CS4 to update Acrobat from 9 to 9.1. Or I could remove Acrobat from my mac.... hmmmm.. what to do, what to do...  
(Version 9.1)