Since there are several different methods for creating content in Jive, I wanted to briefly touch over each of them. From the front end of Jive, we have a direct side by side comparisons of the Native Jive Documents (i.e. docs not created within Office). However, after a certain size it will stop allowing you to run direct side by side comparisons, because the performance impact is too great. So instead it will simply allow you to see each revision of the document, but it won't highlight the changes that they made. Now for uploaded files, it does not offer any revisions or side by side comparisons at this time. In regards to Jive for Office, it does keep a copy of these changes being made, but it's solely for the purpose of identifying collisions and letting you merge your changes with the ones published by another user. You can read up more on that at the bottom of Working with Shared Office Documents. Although this is not something we can provide at the moment, I would at least recommend voting on Support changes comparison for documents posted through Jive for Office. It's always possible that we can build out this feature for a future version of Jive.
Hope this helps.