Method 1: Install Acrobat Reader 6, then Trim out all the extraneous plugins. The same method apparently works with Acrobat 5, if you still have that.
Method 2: Downgrade to Acrobat
4 5.05, which does all the essential PDF-reading stuff, but is smaller and quicker.
OldVersion.com is a boon for finding old versions of freeware. For years I used ICQ98, since it was tiny and advert-free. I’m such an early adopter I have a 7 digit ICQ number 🙂 Now I generally use Trillian, since it’s multi-IM-standard, so I can talk to people on MSN and ICQ and Yahoo with only one multi-megabyte IM program sitting in memory.