Sort of, yes. To "back out" often suggests that the decision to pull out is before the thing has even started, and is often used to suggest that the decision (to pull out) is due to being scared, nervous, ill-prepared etc. Imagine that you enter a room and don't like what you see; you then slowly step backwards the way you came in until you have left. This is "backing out". If you're in the room but later on you simply decide you need to leave at some point, this would be "pulling out". But mostly they are used interchangeably - at least people will understand you whichever is used.