I can only speak for the Palm platform, but you can do it with a number of different free (bundled with a Palm) or purchased (Quickoffice) software packages. My last year at school I took all my notes on my Palm with a Stowaway keyboard and just synced them up with Word. Excel syncing is available, too. I had dozens and dozens of docs dozens of pages long on only an 8MB PDA, so you should be fine.
The PocketPC can do the syncing with Word and Excel docs as well, but I don't have any extensive personal experience with it. It shoudl be at least as functional as what's available for Palm.