In Acrobat, how the first view (e.g. full page, 100%, screen width, etc.) is determined by one of two things. One, if you have Acrobat professional, you can set how your document opens on the user's screen. Two, the user's settings in their own browser determines how the view opens. Without the professional version of Acrobat, I don't know of any way to control how a document opens in an Acrobat reader.