The default for iCloud Drive is that your documents are both on iCloud Drive and on your Mac (Finder "Go" menu > iCloud Drive). That should always be the case unless you turn on the Optimize Mac Storage option. If that option is on and you turn it off, your documents should sync back to your Mac. See the description below from Add your Desktop and Documents files to iCloud Drive - Apple Support
If you need more space on your device, iCloud Drive can help. On your Mac, choose Apple menu > System Preferences. Click Apple ID, then click iCloud. On macOS Mojave or earlier, choose Apple menu > System Preferences, then click iCloud. Turn on Optimize Mac Storage. Then your Mac keeps all of your recent files on your computer, but keeps your older ones only in iCloud, ready for you to download when you need them again.