Inconsistent book trim sizes
Recently I printed a second proof of my 8.5"x11" book after making a small edit. The original proof was 8.5"x11" which looked good on the inteior, nothing was trimmed out. The second proof is 5/16" narrower. I downloaded the LuLu template, and kept everything inside the "live area".
How do I know that this will not happen again in the future?