What is the workflow between iWork apps with iCloud?

iWork for Mac, at the time of writing of this post, has not been updated to work with iCloud.
Last version on the App Store came out in July, 20th, and does not have iCloud integration.

Meanwhile, you can upload and download documents from this page, which is a web interface to iCloud. The process is described in this guide.

There is no iCloud-enabled version of iWork '09 on the Mac as of yet. Right now the way to save to iCloud from the Mac iWork apps is through the website.

Enabling iCloud for iWork for Mac is a bigger deal than I think most people realize. We've still yet to see any sort of UI for saving documents to iCloud on a Mac. So, for example, in iWork, will you see a standard "iCloud" folder in the Finder? Will you see a UI pane similar to the iOS versions of the apps? But in that case, how can you save a standard file to on your computer? Apple hasn't yet answered these questions, and I believe they are still working out some of these major details.

Aside from the UI issues, the Mac versions of iWork still have more advanced capabilities than the iOS versions. My guess, and hope, is that Apple will not enable cross-platform iCloud auto-saving until they are sure that changes will persist exactly across both platforms.