autodoc used to be the more common documentation generator, but these days it is mostly just used for Clojure itself (and is optimized for the task). I highly recommend that you use codox instead. It is excellent. You can see it in action in one of my own projects here
(I know this has been said in the other answer, but for my answer to be complete I need to add it anyways)
Also, in leiningen 2 there is no :dev-dependencies
key. Instead, there is a :dev
profile. Take a look at the Leiningen profile documentation for more information. In this case, all you need to do is add a :plugins
key to your project or global user profile with the plugins you want (like codox, autodoc, etc).