You can now add a 4-digit PIN Code to the OneDrive app to prevent people from using the app to view, edit or delete your files.
Open up the OneDrive App > tap the three horizontal bars found at the top left hand side of screen. Then tap Settings (found on the bottom of the screen) > Options.
Tap PIN (to turn the option ON), then enter your 4-digit PIN in the spaces provided.
Now when you open up the OneDrive app, you’ll be prompted to input your 4-digit PIN before you can gain any access to the files.
Don’t feel too secure with this 4-digit PIN through since it only applies to the OneDrive app. Anyone who uses your phone can still gain access to your files via the Office app (which provides access to all your documents on OneDrive) or the Photo hub (which provides access to any photos that have been uploaded or stored on OneDrive).
I tweeted this deficiency out on Twitter, to which I received the following reply from @onedrive: