The latest update for Documents does not support iCloud.
The fix is submitted to the App Store and will be live shortly.
This is not a bug on our side. For some reason, the compilation process in Xcode went wrong, so the iCloud tab disappeared for those who updated.
We're sorry for temporary inconvenience. Our team has already fixed everything. Let's hope that Apple will approve the update fast.
Do not hesitate to contact us.
P.S. Image Credits — TUAW.
Update: It's fixed now.
