Within Teamwork Desk, you can see previous versions of each article, by clicking the revisions tab.

Revisions allow you to see each change that has been made to a doc, from the very first change right up to the most recent.

The revision tab can be found on existing articles you are editing:

You can then see a list of previous versions which include the date they were revised and which version is currently active:

To the right of the page you will see who made the revision and there is an option to view previous versions.

When viewing a previous version you can choose to make that the current one by selecting 'Restore':