It would seem bizarre to launch a document handling app on the TouchPad - especially one included as standard on the device - and then not allow anyone to actually edit documents in said app. Heck, even Windows had the dismal Notepad and Wordpad programs to torture their users with, whilst HP decided that QuickOffice wouldn't have any editing capabilities on launch.
Well, according to the folks at PreCentral.net, QuickOffice has had an update that does indeed allow document editing. If you don't see the update in the Software Manager on your TouchPad, then try a full reboot - they turned up for me when I did that. I had a quick play and it worked with a plain text file, but not with PDFs (it just launches the read-only Adobe Reader - also just updated today - for those).