Boots for the salt would be a very wise choice to prevent burns.
Unless they're spending extended periods out of doors where they can get wet, or you actually notice them shivering and reacting to the cold, I wouldn't worry about jackets for them. If you're just walking them, they should be okay. Jackets for larger, coated breeds can end up being a detriment, as the dogs can overheat during physical activity.
If the weather is such that they can get wet when it's that cold, then yes, I'd consider some sort of rain slicker or similar, to keep them from getting wet. If they are dry, they should be able to regulate their own body temperature provided they're being active.
Remember that this breed often herded high into the mountains, in temperatures very similar to what you're experiencing, exposed to the elements for most of their lives. Unless they've got a faulty coat [not double-coated], or you've artifically altered their coat in some way [extensive de-shedding procedures, or clipping or cutting their coat], they can keep themselves warm enough on a walk.
GSD and GSD-mixes run the Iditarod every year, without jackets, just fine. They even sleep outdoors in the weather, in beds of straw, during the race.