Today (the 6th of January 2015) Microsoft announced that Office Preview for Android also runs on Android 5 (Lollipop). I decided to give it a go!
First off Nexus 7 (2012) needed the latest image Android 5.0.2 which can be found here where all Google Nexus stock roms are available. Read how to flash a Nexus device.
The next thing to do was to install Office Preview. I opened Google Play app and looked for Microsoft Office Preview (which is available only for beta testers!).
In case Microsoft Office Preview for Android is not found here are the download links: