Are you running DTPro from the “DEVONthink Professional.dmg” file? In that case you don’t have to do anything. But it would be better if you drag the application from that disk to your applications folder.
If you have done that, you can just drag it from there to the Trash. Later, if you decide not to keep our Pro Office version you can drag that to the trash and copy the original Pro from its disk back to your Applications folder.
You can always download any of our versions from our website when you need it. Or burn a copy to CD/DVD.