UPDATE: This is a Leopard Only Tip. Sorry about that.
Creating a multipage PDF document can be a pain in a program like Adobe Illustrator, Photoshop or Lineform. It almost always requires some kind of work around, but there is a much simpler way to create multipage PDF documents on your Mac.
Simply open Preview, starting with the first page that you’d like in your document, then drag the other pages you have created into your Preview sidebar in the order you would like them to appear.
Make sure all of the pages are highlighted, then go to File>Save As> and name your document, then select PDF from the drop down menu.