How do I sync iCloud iWork documents with Lion?
Unfortunately, Macintosh does not (yet) support complete iCloud synchronization for documents. We can only hope that Apple will implement this at some point soon.

In the mean time, go to http://www.icloud.com/ and sign in. You can drag documents to and from the appropriate section on your computer, and it'll work with your iPad. There's still another bug, which involves Mac > Mac syncing, but as long as you just do iPad > Mac or Mac > iPad, it'll work fine. :)

Also, there is a folder located at ~/Library/Mobile Documents/ which contains your iCloud-enabled apps' data. This includes the iWork suite, but unfortunately iWork documents aren't saved as the normal filetypes (e.g. ".pages"), so they can't be opened on their own.