Upon reaching level 70, you must increase your level caps through reincarnation or rebirthing. By doing this, you'll unlock the next level for the job you're currently on, but your job will also be sent back to level 10. Each job's reincarnation and current level cap is independent from each other. You can see your progress in the status window ( + and click the Attributes tab).
The Reincarnation Instructor is located at X:162 Y:172 in Eversun City inside the Dojo. By talking with him for the first time you'll get a free Reincarnation Stone.
To perform a Reincarnation, you need to be at the current level cap for the job you want to use it on, and have a Reincarnation Stone + 250,000 gold for each level up to level 75.
For each reincarnation a job has done, that job will get one extra stat point every five levels. This means that on the first reincarnation you do, you'll have 12 extra stat points at level 70. On the second reincarnation, you will have 24 stat points at level 70. By level 75, you will have 65 extra stat points.
Skill points per level will remain the same. You will be able to use an extra Item mall spring at levels 72 and 74. The amount of EXP Credit Cards required at each level cap will increase, but you will get more Full EXP Credit Cards at the same time. You may be able to unlock skills that would have required reincarnation.
This will also unlock the Beast Mode.