Q: The file “Untitled.pages-tef” couldn’t be opened.

I've had the same problem when I bought a new MacBook Pro.  So many things didn't work from iCloud, including all my Numbers files that were somehow saved as .tef extensions, Mail, iChat, etc. When I checked the AppStore I saw my previously purchased Mountain Lion App waiting to be reinstalled on my new Mac.  After reinstalling, everything came back just fine.

Questions that have to do with iCloud is better asked there.

This is the answer!  Thank you!

Thank you Kreklo! I've been trying everything these last days without success.

Your solution seems to have done it for me. Pages 5.0 now reckognizes its own files. What a relief!

Great help here, thanks Kreklo.

I just unchecked Pages and Preview from System Preferences/iCloud/Documents and Data-OPTIONS (Apps that store documents and data in iCloud will appear here) 

saves great...

Kreklo,  Your tip worked for me.  Thanks!  Does this mean that I cannot use the 'cloud' for my documents?

kblaquire,

Thanks, but your idea would not work under ANY save name.

Hi Wnlight. Everything is been fine with my iCloud documents since then. With the exception of the occasional issue of having to select which specific document to keep because of changes made to the same document on different devices.  Nothing too terrible to work with though.