If you work with the Track Changes function in Word, you know that you can't track the changes if it is not turned on - or can you? If you still have a copy of the original document, you can:

With the edited document open, choose Tools -> Track Changes -> Compare Documents. In the Choose a File dialog box that appears, navigate to the original unedited document and click Open. A new document will appear with every change made between the two documents highlighted or, in Print Layout view, commented. All you have to do now is work on that new document and choose Tools -> Track Changes -> Highlight Changes and be sure that you've enabled the Track Changes While Editing option so that any changes you make from now on are also tracked.