|Files Connect available in: Enterprise, Performance, Unlimited, and Developer Editions|
Users can access Office 365 files from the Files list. Excel, Word, and PowerPoint files are opened directly in the appropriate Office 365 mobile app and when the user finishes editing the document, she can switch right back to Salesforce1 with a tap.
Office 365 files are included in the Files list if your organization has Files Connect set up and you have connected file sources. See Access and Share External Microsoft and Google Files for more details.