Well, maybe I was too short in my first answer (or am _I_ getting *you* wrong?) ... anyway:
the thing that you downloaded from Adobe in fact _is_ the reader software for PocetPCs - _but_ it's not an exe, you simply copy onto your device (or maybe you downloaded it directly onto the PPC?), and it would run there.
Shure, it's an .exe file - but not for PPC. It's one for Windows, to be run on your desktop computer - as an installer for the PPC.
So, if you don't have it already on your workstation, move it there;
connect your XDA with ActiveSync to your desktop machine;
start the downloaded .exe on your desktop;
let the upcoming install shield lead you through some dialogs;
then that program will do the installation of Acrobat Reader 2.0 for PPC onto your XDA;
if the XDA asks you something, answer accordingly;
It also installs some converter into ActiveSync, that tries to optimize transferred .pdf files for display on mobile devices (well, I switched it off ...).
But beware: as good as the Reader for PPC is (at least imho), it needs a lot of space (some 8MB).
Let me know, if I understood you completely wrong.