If you're tired of the backup files created by iWork, simply go to Preferences » General (in each of the iWork applications) and then uncheck 'Back up previous version when saving' and check 'Save new documents as packages.' This will maintain the data needed for Versions and AutoSave without cluttering up your Mac with duplicate files.
[crarko adds: This seems to work as described in Pages; I don't necessarily mind having the backup file.]

