Any character can level as many or as few jobs as they want, regardless of what they started as. You just have to equip your desired job's tool. For example I started as a Conjurer, I got a needle and weaving wheel to become a Weaver and needed cloth so I picked up an axe and scythe to become a Botanist.
If you are in a city with a guild for that job, go to that guild to buy the tools. If there isn't a guild in your city, go to the merchant districts (marked with red pins) and look around for a vendor that sells them.
When you equip the proper tool you automatically become that job, and you can do this anywhere you are not in Active Mode.
Edited, Sep 3rd 2010 10:16am by hints