In case you have a longer document that you want to read, you have a few options available to make the text larger. 

1. On macOS you can set a larger text under Preferences -> Appearance -> Additional options -> Use large text size
2. We are actively working on our web application, but in case you have something that requires longer reading, you might want to try zooming via the browser: https://docs.craft.do/
3. On the macOS, you can enable an option to Zoom under Accessibility:
   

Note: Currently, it is not possible to change font sizes in the iOS app.