A softener can deal with iron if it is dissolved ("clear water") iron (ferrous iron Fe++), and as long as the iron concentration isn't too high. Assuming that is the case, yes, iron out salt is a good idea. Iron is grabbed (as is hardness) by the softener resin, but the resin doesn't like to let go of the iron during regeneration. The iron out salt includes an acid that helps knock the iron off the softening resin. If it is ferric (Fe+++) iron you're dealing with, or if the iron concentration in your water is too high, you'll foul the softener resin.
