Apple announced that iPad pro with 12.9 inch will be released some time in the month of November, but the users of this device iPad Pro need to subscribe Office 365 especially who wants to edit the Office files. Where as current iPhone and iPad users can edit the Office files as per they required without subscription Office 365.
Microsoft confirmed to Ars Technica that the larger screen for the iPad Pro means that the tablet exceeds the 10.1-inch limit for a “true mobile device”. Thus, the Office 365 subscription is needed for editing files on Apple’s next tablet.
At the moment, the End User License Agreement (EULA) for the Office iOS apps does not mention this screen size restriction, but it’s likely that Microsoft will update it before the iPad Pro is launched. As mentioned above Apple is in a plan to launch iPad Pro with 12.9 inch in the month of November as per reports.