Ugh. I need coffee.
Rereading it...it's width not length. Still applies across the board, not necessarily to this pattern. It is also much easier to remove the seam allowance then it is to work with it.
Grade the pattern like you normally would. If this is adding 1.25 to all 4 seams or doing it in the width and length, you need to do that.
Once that is done, redo the pleats, and be aware they will be wider at the base then original. Not much, really, but it is a slight difference.