Many times the pattern you have chosen may not be quite big enough in a few places.  Most of the time you can add a little width at the side seam, either all the way down from the armhole, or tapered out just where you need it.  For example, if you need a little more room in the bust, adding a quarter inch at each side seam (front and back) will give you a full inch.  You will also need to add that extra width at the sleeve seams, giving you an extra 1/2" fullness.