So, on the Preview, you have the box for Show Margins checked, right? By the way, my Preview screen shows black lines, not blue ones. So, I hope we're talking about the same lines. If you uncheck the box for Show Margins, those "blue" lines disappear, right?
Also, I do not have an "orientation tab". If I click Page Setup on the Preview screen, I have the option to select Landscape orientation on the Page tab. Can you tell me exactly where the "orientation tab" is?