I am using Cerience's Repligo software upgraded to WM 5.0.

Seems to work well on the treo 700W so far. It uses only a little memmory and my 97 page Repligo file is viewing with no problem. You create the repligo file on your desktop (Word and Excel are particulary easy, but any program will work including adobe), transfer it to the Treo and view. It is not a memory hog at all. Cerience has a free trial. Make sure to download the very ltest version, since earlier versions are not WM 5.0 compliant.

This may be a lower memory alternative to .pdf files.