how do i remove documents from icloud drive?

If you are only using iCloud Drive (without the Desktop and Documents option) then on your Mac you can open the iCloud Drive folder in Finder (one way is to use the Finder "Go" menu in the menu bar at the top of the screen) and move them to another folder the same way you would move any other files in Finder.

If you have the Desktop and Documents option turned on, see the following from Add your Desktop and Documents files to iCloud Drive - Apple Support

Turn off Desktop and Documents

When you turn off Desktop & Documents Folders, your files stay in iCloud Drive and a new Desktop and Documents folder is created on your Mac in the home folder. You can move files from iCloud Drive to your Mac as you need them, or select all of your files and drag them to the place you want to keep them.

1. From your Mac, go to Apple menu  > System Preferences > iCloud.
2. Next to iCloud Drive, click Options.
3. Deselect Desktop & Documents Folders.
4. Click Done.

If you turn off iCloud Drive or sign out of iCloud, you have the option to keep a local copy of your files that are in iCloud Drive. Whether you decide to keep a local copy or not, a new Desktop and Documents folder is created in your home folder. If you choose to keep a local copy, your files in iCloud Drive are copied to a folder called iCloud Drive (Archive) in your home folder. Then you have the option to move any files that were in your iCloud Desktop and Documents, back to your new local Desktop and Documents.

See the article https://support.apple.com/en-gb/guide/mac-help/mchl1a02d711/10.14/mac/10.14

Move items to your Mac and remove them from iCloud Drive

• On your Mac, drag items from iCloud drive to another folder in the Finder sidebar or on the desktop, such as Downloads, Movies, Music and Pictures. 
• The items are copied to your Mac and removed from iCloud Drive on all your devices set up for iCloud. If you change your mind, you can drag items back to iCloud Drive.