Word scaling actual document by 71%, not just print

Have a self-publish book in Word ready to export to .pdf. Except it is in A4 format and not the required A5 (ie requires a 71% rescaling). Fonts are set to styles for this document only so do not carry over.

Yes I can print two pages to an A4 which I have used to modify font sizes to suit A5 pages.

If I set the page size within the document it retains the original A4 font.

I need to set the page size to A5 (with all font/para/margins setting reduced by 71%) so I can incorporate the required bleed margins before I Export to .pdf.

Surely there must be a way to achieved this. Have I missed an obvious setting?

Any help or suggestions very welcomed.

Tony