Sometimes you need to work with a document which was created in a previous version of Word. Then you must work with Word 2013's compatibility mode.
However you can convert your document to a Word 2013 document; that will convert the document format to the docx format in Word 2013.
The older version of documents may have some difficulty using the new features and being modified in Word 2013. But converting a document will also clear all compatibility problems.
To convert a document from a previous version to the new Microsoft Office 2013 format use the following procedure.
First of all open your older version of Word document in Word 2013.
Click on the "File" tab.
Now choose "Info" and then click the "Convert" button.
Note: Now your older version of document is converted to the Word 2013 format.
However you can also create a new copy of the older document and save it in the newer version of Word format.
Use the following
Click on the "File" tab and choose "Save as".
Enter the new document's name in the filename box and select Word document in the "Save as" type drop down list.