I have been using Repligo for a couple years now, and it works on WM5 as well as WM2003SE.
It comes in two flavors, a viewer and a "creator". The Repligo creation tool costs a few bucks, but is certainly worth it as you can convert any document for viewing, reading, etc. on your PPC.
I've found it is certainly clearer to see/read than Acrobat Reader on the PPC, and a bonus - you don't have to create "tagged" files, and you can convert existing Acrobat Reader [pdf] files. The creation program will also sync Repligo files directly to your PPC via USB without using activesync [puts files anywhere you want, yes even on a CF/SD card].
Anyway, it's one of my "can't do without" programs that has at least for the Axim, replaced Acrobat Reader. It's at
http://www.cerience.com, and no, I don't work for them. It's just an excellent alternative to Acrobat on the PPC.