Nowadays, we store files in different cloud storage such as Google Drive, Box.net, Dropbox, OneDrive, etc. By default, Outlook allows users to insert a file from OneDrive, but you need to authorize ...
The only real option is to jailbreak your iPhone and use sideloaded apps that allow you to download exactly what you want. Another is to use a free iOS file manager app, such as Documents by Readdle.
iOS 11, released on September 19, introduces major design changes, new app features, and a complete interface overhaul for the iPad.