Well, these didn't work for me. After poking around a bit I found something that did work, at least for me. This may apply to others as well. Like many folks, I've had an Apple ID for quite a number of years. Then, when Mobile Me came along, I bought in and have had it for a couple years. Then along comes iOS5 and iCloud. Probably like others as well, I didn't want to take a chance disturbing my Monile Me data and so I signed up for iCloud using my original Apple ID. This seemed to work well except for the same symptom with Numbers/Keynote/Pages, i.e., no documents would synch with iCloud. I tried all the suggested fixes with no luck.
I got to thinking maybe it had something to do with having multiple iCloud accounts, for me it was the one I first used using my original Apple ID, and the one that came along with my Mobile Me account. I had both email accounts on my iPhone and iPad but only one with documents enabled.
Here is what worked for me, delete all but one Apple ID//Mobile Me account:
1) Settings->Mail,Contacts,Calendars
2) Select iCloud/Mobile Me account that is the duplicate.
3) Delete the account. This will remove all the associated data with that account. Can't be helped.
4) Delete Numbers/Keynote/Pages from you iDevice. Not positive this is needed but it is what I did.
5) Hold down the Sleep button to turn off, then turn back on your iDevice. Again maybe not needed but I did it.
6) Settings->iCloud->Documents & Data: slider ON
7) Reinstall Numbers/Keynote/Pages. I did it directly with an App store re-download.
8) Settings->Numbers/Keynote/Pages (each in turn) Use iCloud slider ON
9) As you start each Numbers/Keynote/Pages, you "should" get the welcome screen and a Use iCloud button. Be sure to select it.
10) If you had the same problem as I, your documents will synch with iCloud across your iDevices.
Hope this helps some of you!