When I installed my Adobe Acrobat Pro v.6, it didn't go near that folder. It just set itself up in its own directory.
Are you going with the defaults for the installation or are you trying to change the target directory? Normally it puts the pdf's in the individual's document directory.....
If you use the PDF print drivers (allows you to print a PDF file from any application, which is not installed by default in my version 5) and you get a similar error (Can't write/access default user.....) simply re-install the print drivers using the Adobe installation disks. No need to re-install the whole application. I get that error every so often. They may have fixed that problem by now.