Do you have it turned on in both places.
Settings > iCloud > Documents and Data
and
Settings > Pages; Use iCloud.
If so, try turning both off, then back on in the order listed. You may end up with some duplicates.
You'll want a good internet connection for the first sync.
[Edit] OK, when I went to iCloud via the Web and tried to open iWork, I keep getting a popup, "Cannot open iWork" and my options are Report to Apple, OK or Try Again. I guess something's messed up in iCloud.
Haven't seen that before, though I've seen individual files mess up. That was before Mountain Lion. So far, I've had no problems with the new OS, but it's been mere days.
I assume you're going to talk to Apple as suggested. Please let us know how it turns out.