There is a catch, though - it only runs on smartphones. If the app detects you are working on a tablet, it will refuse to install. That's unfortunate, because even 5 to 5.5-inch smartphone displays still feel somewhat small for comfortable document editing. But we assume owners of the Xperia Z Ultra and similar tablet-phones will be pretty happy with Office Mobile.
MS's mobile Office suite is integrated with OneDrive and SharePoint, supports editing of documents from e-mail attachments, and is designed to look as good as possible on small screens. A particularly nifty feature is Resume Reading - When opening a Word document from OneDrive or OneDrive for Business on your phone, it automatically resumes at the place where you left off reading, even if you last viewed the document on your PC or tablet. It's little gems like this that make Office work more comfortable than ever.
You can find Office Mobile in the link below.
Download Office Mobile (free): Android