Tracking changes in Word documents https://support.office.com/en-us/article/Track-changes-in-Word-197ba630-0f5f-4a8e-9a77-3712475e806a#ID0EAABAAA=Office_2010
Instructions
Turn Track Changes on and off by going to Review > Track Changes.
When it's turned on, deletions are marked with a strikethrough, and additions are marked with an underline. Different authors' changes are indicated with different colors.
When it's turned off, Word stops marking changes, but the colored underlines and strikethrough are still in the document.
To review the changes in your document, go to Review > Tracking > Display for Review.
To review the changes, indicated by a red line in the margin, choose Simple Markup.
For a detailed view of the changes, choose All Markup.
For a preview of how the document will look if you make all the suggested changes permanent, choose No Markup.
To view the original document as if all the suggested changes were removed, choose Original.
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