Track changes in Word 2013 works in exactly the same way as it always has except that there is now another option for viewing any tracked changes. The new option is the default view for how tracked changes are viewed and is referred to as Simple Markup. If any changes are tracked in a document a red line is displayed in the left margin of the document to indicate a change – click the red line to view the change.
If you prefer tracked changes to always be displayed in a document you can change the markup option on the Review ribbon to be All Markup.
If you close the document whilst All Markup is selected, the next document will open as All Markup by default.
