The idea behind a PDF is that it cannot be modified once it's turned into a PDF. totally self-contained and uneditable. So the only way to change something like this would be on printout, either by rearranging by hand or adjusting print order if it lets you.
or purchase Adobe Acrobat 5 full version. Then you can do it. <whisper>i have also heard about this thing called acquisition. it my help. check versiontracker.com. good luck </whisper>