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 revisions 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.
For more information see: Changing the appearance of your Help Docs site