Check the preview before you print
Because scaling changes both effective font size and margins, always check print preview after adjusting the percentage β text that looked fine at 100% can turn awkwardly small or clip near the edges once scaled up or down.
A different problem from calculating an enlargement ratio
This walkthrough covers Word's built-in "Scale to Paper Size" dropdown, which does the ratio math for you automatically. It is a separate question from working out the raw percentage a copier needs to blow up a document from one ISO paper size to another (why A4 to A3 is 141%, not 200%) β that calculation is covered elsewhere, since Word's own print dialog does not require you to compute it by hand.
Frequently Asked Questions
Does scaling the print job change my original document?
No. Print scaling only affects the printed output; the page size and layout saved in the actual Word file stay exactly as you set them.
Can I scale just one page instead of the whole document?
The scale-to-paper-size option normally applies to the entire print job, not individual pages. If different pages truly need different sizes, that requires section breaks and page setup changes in the document itself, not print-time scaling.