If you're using up-to-date versions of the apps on both your computer and your iDevice, then you will be able to access the same files ...
- using the web interface to iCloud from any computer
- using the app on your computer
- using the app on your iDevice
You will need to check whether the exact model of refurbished iDevice you're buying can run up-to-date copies of the iWorks for iOS apps. Check with