Many projects require modifications to the house plans. What if I need the help of a professional draftsman or architect? What do I order when I need to make several and/or big changes? You, my friend, need a CAD file.
It's amazing what trying to save a buck can cost you. Here are a couple of examples of DIYers I have met that [I'm sure] paid much more than they had to just because they wanted to save a buck on house plans.