Dec 10th, 2014 It’s now possible to edit Office documents using Gmail
The app lets you work with any spreadsheet, whether you have an internet connection or not. Plus, once you finish working with no connection, you can still save changes to upload to the cloud as soon as you get a connection.
Just like on the desktop version, with the official Google Sheets app all the changes you makes to a document are saved automatically, so you'll never lose anything. It doesn't matter if you run out of battery or the app closes, everything will be saved.
Google Sheets is a great tool for working with spreadsheets that will certainly prove very useful when editing documents shared with other users.