Is there anything I can use as a substitute for hoisin sauce that's less salty or even salt-free? This is for a sauce to go with pork steaks.
Hoisin has a few primary flavors: salt, sweetness, and umami. If it's a significant part of a recipe, leaving it out isn't really an option; you'll notice the lack of all three of those.
If you can find a fermented soybean paste that has less salt, that'd be the closest substitute, possibly with some added sugar. Otherwise, you'll have to look for other umami-rich seasonings, and again likely add sugar. See What is a good vegetarian source of umami flavour? for some ideas. You could also use things like bacon or anchovies since your case doesn't have to be vegetarian. Of course, anything with a distinctive flavor of its own isn't going to be an exact substitute (anchovies don't taste quite like fermented soybeans), but at least you'll have a sauce in a similar direction.
Unfortunately, Hoisin sauce is one of these Asian ingredients that is always salty, whether you choose brands like Lee Kum Kee (more processed) or Koon Chun (more raw). If it is included into a sauce which has many more ingredients, where Hoisin doesn't bring too much character into it, and I've seen a lot of those, I would just skip it. If not, you can always grab a recipe of the sauce on the internet, there are quiet a few, and see if you can lower the salt factor from the ingredients it is made of. Bean paste and soy sauce are there, but I also have seen molasses, miso paste, and even peanut butter.