It doesn't mean exactly the same as academic, although academic writing styles can indeed by pedantic (although not always - depends on the subject). You can be pedantic in the way you write fiction, or the way you chat on a forum. I am described as pedantic - and the way I'm writing here would be seen by some as pedantic, and in fact I'm deliberately trying to do my pedantic style more than normal, so you can see it. See how I try to logically distinguish here between 'academic' and 'pedantic' and all the possible combinations - I try to be exhaustive in the explanation, and I spell things out where it is probably not always necessary.
Also, pedantic, in a forum setting, might be if someone said something where they weren't quite exact, but everyone knew what they meant, and then someone corrected them. The correction would be pedantic, because the meaning was clear even though the exact words weren't accurate. Pedantic is focusing on the tiny details and not on the big picture - which is a typical autistic thing to do. And it's likely that people might get irritated with the pedantic person and tell him he was pedantic, and he would argue back that he was being accurate and that accuracy is important - and that argument too would be seen as pedantic, because a non-pedantic person would just let it go and not care.
A further pedantic thing to do would be to answer a simple question in great and probably unnecessary detail, as I have done here, and to then link to a further definition, which I will also do: http://en.wikipedia.org/wiki/Pedantic. Note how it describes how pedantry is related to autism. (Another example of pedantry is that I first wrote 'pedanticness' and then thought it looked wrong and then checked in my dictionary to see what the word should be, and then changed it to 'pedantry'!). People get very annoyed with this style of writing, by the way, because they think it is far too much unnecessary detail. People are often annoyed with me when I write like this!