Like many horror sequels, Hellbound: Hellraiser II attempts to up the stakes and the scope of its predecessor. In the attempt, it manages to walk the fine line between "expanding the setting" and "explaining too much." All the same, now that we understand a bit more of what to expect from Cenobites and skinless undead, the scariness is diminished—its vacancy filled with extra gore and weirdness.
Hellbound picks up soon after the events of, and includes several flashbacks to, the first Hellraiser (my review is here). I assume the intent was to make the film comprehensible to those who missed the first one, and indeed, so thorough is the recap that this is one case where I doubt you'd miss much if you went straight to the sequel. It might feel more WTF than it already does, though, and plus you'd miss Andrew Robinson (the dad in the first movie), who doesn't reprise his role here. The only other principal who doesn't return is the boyfriend, but maybe he died in the last movie…I didn't care enough to commit that detail to memory.