Help creating printing action in CS6
What you might consider doing in your action is to go to Image->Canvas Size and adding the 1/2 inch or whatever you were looking for all the way around it.
If the result was then too larger, by an inch in each direction, then go to Image->Image Size and specify the desired long dimension.
I do this when I want to create "galley border" around the image. In my case, I add 1/2 inch around top, left and right and 1.5 inch to the bottom.