Microsoft yesterday released the updated versions of Word, Excel and PowerPoint apps for iOS devices. This v2.12 update comes with improved support for the Files app. With this support, you can now use ‘Open in’ with Microsoft Office documents from Apple’s Files app on iOS. Previously, you were able to only ‘Copy to’ the Microsoft Office apps.
iOS keeps track of which apps you open documents in, per document type, with the share sheet.
When apps support Open in Place, the system can decide to automatically open an app without displaying the share sheet first.
— Ian McDowell (@ian_mcdowell) April 9, 2018
This update also includes improvements for speed and reliability. You can download the updates from App Store.