Hi Joy W,
I am a Microsoft products user like you are and I will try to help.
To print A4 to A5:
For Mac: Open the document, then File > Print > Paper Handling > Scale to Fit Paper Size > Destination Paper Size > Select 'A5' here
For Windows: Open the document, then File > Print > Paper size (drop down arrow) > Select 'A5' here
Kind regards, Amit