One of the ways to enjoy the big screen of Nexus 7 2013 is increasing the font size of the device. The font size varies from small to huge and to change the font size on your Kitkat running device, do as follows:
1. Open Settings application
2. Under Device settings, open Display.
3. Tap Font Size and select one of these options: Small, Normal, Large, or Huge
Note that, the default launcher of Nexus 7 doesn't let you change the entire font of your device by default. To know more about how to change fonts on your Android device regardless of its Rooting status, read: How to Change Fonts on Android