In Page Format for Score, you can scale the whole page, and you can systems.
Furthermore, system scaling comes from two numbers that are multiplied, the staff height and a percentage, which produce the Resulting System Scaling.
So, a few questions about this:
Does it matter whether you change page scaling or system scaling? Does 100% page scaling with 48% system scaling produce the same result as 48% page scaling and 100% system scaling? For system scaling, is there a rule that certain staff heights and scale percentages work well together?
If you create a new score with the Setup Wizard, Finale fills in the page format with sensible values, given the page size and the number of staves you have specified. But is there a reference list somewhere of “good settings” that can be reused?