The version doesn't matter as long as it's above 2007. All the files generated from version 2007, 2010 , 2013, etc are inter-compatible. This means you will have the possibility to open the files in 2010 even if they are generated in the 2013 version. The same procedure works for all the files generated within Microsoft Office's packages. This simple compatibility makes editing easily between client and users with different versions of Microsoft Office.