Unless you mean buy songs through spotify (in which case you probably wouldn't bother with premium) then no. The downloaded playlists aren't stored as tracks that you can get hold of.
You can use a variety of audio rippers if you desire (audacity for example) but its a fairly slow process, fiddly and the quality at the end will be something like 128kbps. I use it occasionaly to make mix cds for the car but otherwise you're better just buying the tracks (or straight up piracy).