Not sure how I really manage it, but sometimes I forget to lock my kindle, so I lean on it move around the the font size is then either too small or too large.
Always winds me up, anyway should this happen to you, or should you want to change it, then click anywhere at the top of the screen, you will then see Aa.
Press Aa, then the 2nd tab will be Font From there you can then select Font Family,,Bold and Size.
I originally was looking through all the settings, but you will not find it under there.
Hope this helps
