How to correctly uninstall an App Store application
You can see exactly what was installed by the appstore with this command:

lsbom /private/var/db/receipts/com.apple.pkg.Pages5.bom


lsbom /private/var/db/receipts/com.apple.pkg.Pages5.bom | grep -v '/Applications/Pages.app' will show you all the files which are not in the /Applications/Pages.app folder (which is actually nothing).

Beware that each new update via the appstore will overwrite this bom file, and not create a version-specific one.  The bom should reflect the current installed files.

Assuming you installed iWork09 from the DVD, then the files in /Applications/iWork '09/ as well as the support files in /Library should not have been affected.