Ability to set the default scale (other than 1=1) for all future PDF docs.
AND the ability to set the scale for each individual PDF docs that will remain assigned to that PDF even if you exit Adobe Acrobat and re-open it. I'm an engineer, and work with various different scales, so it would be very beneficial for each PDF, if the user set scale would remain locked with each document, so you don't have to re-establish the scale after exiting and re-opening Adobe Acrobat.