Thanks to those who posted, and because of the limited scope of my particular situation, this may not be good news for everyone, however this is what I found:
- On the iPad, if you've updated the Pages (or Keynote or Numbers) app and haven't updated the old docs, you can easily swap the old app in and archive or delete the new version (2.0) in Music > iTunes > Mobile Applications.
- If you've updated/converted the existing docs as well as the app, you've gone past the point of no return with those docs and will either have to remake them in the old app once reinstalled, or decide you'll upgrade everything else (Mac Mavericks and Pages etc.) to be compatible. (For us, that would mean spending about 3,000 unbudgeted dollars!)
- With Apple Configurator and our managed iPad labs, we were lucky. The updated apps on the iPad server had not yet been deployed onto the iPads on the carts. Downgrading on the server was easy - I archived the new apps and copied in the old Pages etc. apps.
In future I'll do a better job of reading the update notes before jumping to install! I should know better, since the same thing happened with iWork 08 and iWork 09 - not backwards compatible.