Good afternoon Lynn68Mc,
Welcome to the Apple Support Communities!
It sounds like you are having an issue printing from your iPhone or iPad to your Brother printer.
Which printer model do you have?
Have you been able to print from your iPhone or iPad successfully in the past?
Are you printing from a website or from an app, like Notes?
If printing from a website, you don't have any control over the font or size.
If printing from an app, you can change the font size for the document, and see a preview of the text before printing.
The resources below will help you address this issue:
About AirPrint
Use AirPrint to print from your iPhone, iPad, or iPod touch
If the issue persists, please reply to this thread and we'll do our best to help you!
Take care.