A:Answer You can if your playlist contains mp3 files in it.
Personally, I create a new folder and drag-and-drop mp3s into it in the desired order for listening. This can be done using File Explorer on a PC.
So you tailor your own playlist with mp3 files you have on your computer.
I haven't tried to upload my Spotify playlists, but I assume you should "own" the songs you upload to it... so my PC's music library is from purchasing mp3s from Amazon and from the tedious task of ripping all of my old CDs to my PC via Windows Media Player.