I scanned a book a while back to a PDF file. I would like to split the PDF pages in half so that each paper page is on an individual PDF page. The only way I can see to do this is to duplicate the file and crop one copy to the left page and the other to the right. Of course, combining the files would be a tedious process. Is there an easier way? I have Preview 4, Acrobat 8 and PDF Pen. Thanks.