Thank you for your post. In this case the user should be able to open the 2014 file within the 2015 software providing they have all OE’s installed for third party data. Additionally once it is saved in the 2015 format, it will be upgraded. If you need the file back ion 20-14 format, the user will need to do a save-as to the 2014 nwd format for you to then view in 2014 NW software’s. I hope this helps answer your inquiry.
Michael Bussiere II
Support Specialist
Product Support
Autodesk, Inc.