When running a Content Search, search terms are automatically highlighted in the document viewer. The Keyword Search dialog will display at the top of the Index Panel in the document viewer.
The dialog displays the index of the current hit and the total number of hits in the top right corner of the panel. You can move forward to the next hit by pressing F3, and back with Shift + F3. Alternately, clicking the forward and back arrows in the Keyword Search dialog will move between hits.