There are a few ways you can track changes in a PowerPoint PPT file. One is to insert a comment for each of the changes you make – which obviously slows down the editing process. Another way to track changes, and perhaps even more rewarding for both writer and editor than inserting comments, is to compare the original and the edited versions of the PPT file.
Use the Compare option under the Review tab.
This will produce a summary, which, if not as comprehensive as the track changes feature in Word, is pretty good: