Creating local archives of iCloud documents

How can I download archived versions of my iCloud data at will?

iCloud's security is no match for user error, as I have experienced on one recent unfortunate event. Luckily only a few Notes.app notes were affected. In the interest of protecting my works from wildly unpredictable future self, I would like to periodically make manual backups of my iCloud data.

How can I make manual copies of my iCloud data? I imagine I would periodically make a copy of my Notes.app data as I have scores of gigabytes of other data that are not portable.

I have both up-to-date and older versions of iOS and OS X at my disposal -- any solutions regardless of platform are appreciated!