If you click the View () icon next to a version on the Versions tab, the Document version pop-up window appears. If there is more than one version of the document, the dialog allows you to view a side-by-side comparison with other versions of the document.
You only need to select the appropriate version in the Compare to drop-down list. Content of the two versions will be displayed side-by-side with the changes highlighted in red font. You can roll back the document to a particular displayed version by clicking the Rollback () icon in the top-right corner of the version's column.