if you are using wppizza->templates to format the print templates , you can set font sizes there (if you use html)

however, you seem to be using plaintext, where there is no formatting.

furthermore, your screenshot says “sent from my iphone” which the plugin itself does not do, so you are forwarding somthing from somewhere the plugin has no control over and your size issue might be related to that

lastly, it might also be in your printer settings and you may also find if you shorten your “we are closed” text – that one long line of text you have there – it might automatically resize to fit somewhat bigger (in fact, that’s the first thing i would try)