Unless you have the game set on 'auto' the text wont advance until you've press the X button. And if by chance you do skip/miss something, pressing triangle will pull up a backlog of dialog that actually goes pretty far back. There are no actual movie cut scenes so you can't miss anything.
And just incase there's a particular scene you really enjoy, Neptunia also provides an in game event viewer you can use (I want to say) anytime.
And also, questions like this can be posted in either of the two Neptunia general threads rather than making separate threads entirely.