Microsoft has now announced that they are going to pre-install the Office Universal apps in the HoloLens Developer Kit. Currently Word Preview, Excel Preview, PowerPoint Preview, and OneNote Preview are supported. For OneNote, viewing, creating and editing notebooks is free and doesn’t require a Office 365 subscription. For Word, PowerPoint, and Excel, viewing documents is free. You will initially need a Office 365 subscription to edit documents, worksheets, and presentations but Microsoft will remove this restriction for HoloLens Development Edition in the Summer timeframe. Since HoloLens is running on Windows 10, Office team was able to bring Office Universal apps with ease.
Learn more about Office Apps on HoloLens here.