And don't store that backup drive in the same region (area),. Fire, flood, earthquakes, tornadoes have wiped out whole towns or counties.
(You may want stuff to read while you wait YEARS for insurance and building departments to allow you to rebuild. Just ask the folk in Northern Calif.
)
KEEP YOUR OWN LIBRARY COPIES.
3 of the (publishers) stores I bought from back when I joined MR are gone.
Do not direct download to a device from a store (unless you have previously downloaded to your PC successfully). Protected Storage means you can't extract that document via USB.