Originally Posted by eureka
No, you haven't to jaibreak. It will work even on stock non-jailbroken devices.
Thanks, eureka. I've uninstalled jailbreak for KT, and add new fonts following the instruction. The problem is I still got "Your Kindle Needs Repair" after restart. I can get into the system by plugging it into my PC. But all fonts are gone in the Aa menu. Seems this method does not works for me.