If you lack page up/page down and a mouse wheel, Ren'py has an option for you. Go into Preferences and choose "Rollback Side" either right or left. Then if you need to go back, move your mouse to that side of the screen and click anywhere outside the text box. It'll take you back.
Glad you're enjoying it so far!
Thank you! I will check that out. Eventually I discovered (by keysmashing, basically) that function + the up arrow would also work. Wanted to mention it for other Mac laptop people!
I've played through the Sherwood side and am playing through the Nottingham side now -- I really love it. The art is so lovely, the backgrounds are perfect, and I want to romance absolutely everyone!