In Word 2013, you'll see the words [Compatibility Mode] next to the file name on the title bar. Compatibility Mode makes sure that no new features in Word 2013 are available in the document, so that people using earlier versions of Word can work with it. You can work in Compatibility Mode or you can convert your document to the new format. To convert the document, click File>Info>Convert. Converting your document lets you use the new features, but people using earlier versions of Word might have difficulty editing certain parts of the document.