Sure, all ion exchange softeners can use potassium chloride instead of sodium chloride but.... you may have to increase the salt dose. If and how much depends on the salt efficiency setting of your salt dose/pr cubic foot of whatever type resin in the softener. For 6 lbs/cuft, raise it 12% and for 4 lbs/cuft and higher efficiencies (less than 4 lbs/cuft), raise it 30%.
If you have a salt grid/platform, you should remove it.
If you are wanting to do this because of added sodium with the use of regular salt. Multiply your hardness in grains/gallon by 7.85 mg/l. That gives you the added sodium in roughly a quart of your softened water. Then check your loaf of white bread, glass of skim milk or V8 juice and other food/beverages and compare the sodium in their serving size to your quart of softened water. You'll see that usually there is less sodium in your water than common things you ingest everyday. And do you drink a quart of your water per day?