To enable iCloud Drive go to iOS device settings, select iCloud and toggle on iCloud Drive. Make sure Scanner Mini is enabled.
Then open Scanner Mini settings and toggle on Use iCloud to make your files available in Scanner Pro on your other iOS devices.
To turn on iCloud Drive, go to settings and enable Use iCloud Drive toggle. This will enable you to share files from Scanner Mini to other apps.
Note: iCloud toggle is for the 2-way sync with Scanner Mini on other devices, while iCloud Drive exports and syncs through the other data container.