Many word documents are being multi authored, and you may want to track the changes done by different users and then accept or reject them in the final version of the document.
Microsoft Word 2010 has a direct access to track changes over a document, under the review tab over the ribbon interface. So, in order to track the changes done by different users over a word document open the word document and then click the review tab.
Under review tab you will see the option track changes, you just need to click that option on the ribbon interface.
After clicking the track changes option you will see all the versions and changes done by different authors on these versions as shown in the image below.
You can simple accept or reject a change done by different user to make this document final after reviewing all the changes, you can also revert to the original copy of this document without any changes with this option.