The Role Scoper plugin can enable the moderation of page/post changes, with some limitations.
After installing Role Scoper, go to Roles > Options and enable the "Pending Revisions" option. Contributors will now see their own published posts/pages and can edit them. However, upon saving they are notified that the changes have been saved for editorial review.
Administrators see the change as a "Pending Review" post/page, alongside new submissions. However, upon clicking to edit it, they are taken to the Revisions Editor, where they can "restore" the revision.
This functionality would also allow a user to submit changes to others' pages/posts, if their own role includes edit_pages and edit_others_pages, but not publish_pages or edit_published_pages.
The limitations are:
- only Administrators can moderate the Pending Revisions
- there is no prominent indication when new Pending Revisions are saved - only a bump in the Pending count