The last version of Acrobat Reader available is Version 9.5. First grab the last full installer (version 9.4) which, at the time of writing, can be downloaded from:
ftp://ftp.adobe.com/pub/adobe/reader/mac/9.x/9.4.0/en_US/AdbeRdr940_en_US_ppc.pkg.zip
(TODO: I need to mirror the above file somewhere.)
After you've got and installed the above pkg, install the 9.5 update from:
http://ardownload.adobe.com/pub/adobe/reader/mac/9.x/9.5.0/misc/AdbeRdrUpd950_all_ppc.dmg
