Provided Doom could prevent the physical power of Superman, he could easily subdue him with plenty of magic and some advance planning.
Superman is invulnerable to many things, but magic is notoriously one of the things he struggles a great deal with.
Beyond being intellectually superior, Doctor Doom is one of the more magically proficient Marvel villains out there.
If the two were to just meet on the street randomly, however, it’d really come down to how Doom learned Supes’ weakness, and if he could exploit it before Superman took a shot.