How use steamworks sdk in unity free? Do I need unity pro?

I will need to integrate the steamworks sdk with my unity game, I think this is possible because to my knowledge, kerbal space program was made with unity and it is on steam. I would prefer if I could find a solution using the free version of unity. Also if this is not possible with the free version of unity, then could you suggest any other drm solutions I could use with unity free?

To use steamworks you need plugin support and that only comes with unity pro I believe.
And a steamworks ID wich you get after being accepted to steamworks.

Steamworks in writtin in c++ so you also need something like steamworks.net (free) or ludocity’s steamworks plugin (on the asset store but it gave me errors) to talk between your game and steamworks.