This thread explains the best method I know of to do this.
I’d suggest starting with only a few documents at a time with this, especially if they are long.
Another method (actually easier, I think) is to open System Preferences > Printers & Scanners, select your printer in the left sidebar, then select “Open Print Queue”. Then go to DEVONthink and drag your PDF(s) into the Print Queue window, where they will be sent one-by-one to that printer.