The fourth draft wasn't used to shot any part of the film. Its pretty wildly different from the film, containing many sequences that were changed, cut out and heavily refised, and even a look at the dialog itself reveals a pretty different incarnation of the film, close as it may be to the final version--this is no surprise considering it was written six months before production, and even before major pre-production had begun. A version of the fifth draft is available in all those "Star Wars script books", including The Annotated Screenplays itself.