You could do it in a kind of cheating (and very simple) way by having a large text box at the bottom of your intro page, a slightly smaller one above, and so on to the top of the page (looking a bit like a pyramid) and set the font size slightly smaller as they work up the page.
All you need to do then to make the text appear to 'float' up the screen is set the text in the bottom text box and then blank this and put the text into the text box above it, and so on until it gets to the top.
OK so I know this is a wee bit dodgy but there you go; the much easier option, yet slightly more expensive, is to get your hands on a copy of Flax or Swish which will prob. do a nice floaty thing for you. =)
Hope this is remotely useful.
=)
PetitPal.
p.s. the other way would be to chuck some text into a movie clip in your library, then use some code to float it up the screen and re-scale it as it moves...