Score size reduction

I am writing a 23 - line score and I want to fit it on legal size paper. I need to reduce the size of the entire score, but when I go to EditScore Size and reduce it, it only reduces one line of the score even when I select all. I’m sure I’m just doing something wrong, but I definitely need to make my score smaller to fit on a conventional sized paper

The overall size (per layout) is controlled in Layout Options > Page Setup > Space size.
See the User Guide for more details.

Have you set your paper size as 8.5" x 14" in Layout Options (CTL-SHFT-L), and then adjusted the rastral size there until you are happy with the overall look?