I have a folder located within
Program Files\Adobe\Acrobat 9.0 that contains the setup files and takes up a lot of disk space.
Can I remove it safely, and why doesn't the Adobe installer automatically clean up after itself?
you can delete the installer files.
however, if the installation needs repairing you may have to download/run the original installer package again.
to be sure to be sure, move the files to another location first and see whether Acrobat is acting up if the files are not in place, if it does, well move 'em back.
i usually keep those files (e.g. MS Office installation sources, since Office has the tendency to 'break' every now and then) on an external hard drive, and if needed i can copy them back.
Adobe says that it is safe to delete this folder. http://kb2.adobe.com/cps/500/cpsid_50071.html