ERROR: THIS MICROSOFT WORD DOCUMENT CANNOT BE OPENED....

When I tried to open a document in Studio 2011 (transferring to 2015), it send me and error which reads:

"THIS MiCROSOFT WORD DOCUMENT CANNOT BE OPENED BECAUSE IT CONTAINS TRACKED CHANGES THAT HAVE NOT YET BEEN ACCEPTED OR REJECTED"

 

I need your assistance in order to clean the documents or any advise/help/instructions I can get from you to be able to open this document will be highly appreciated