just in case you don't know--using 'rotated' view will NOT rotate the page when you export a PDF--it's a useful function for designing/aligning/positioning, etc-- so you don't have to try to position things upside down--if you want the pages to be actually rotated, you'll need to either physically rotate the content or open the exported PDF in Acrobat and rotate the pages there.
that said--as to why your PDF export is hanging is hard to determine--to troubleshoot--try exporting each page separately until you find the one that's hanging the app--that will narrow down the problem (which could be a corrupt image, a bad font, or similar)
Faster than doing it one page at a time is to try one HALF of the pages at a time, then divide each failed half and try again, until you isolate a problem page, then continue the testing by moving half the objects to the pasteboard.
It's also worth trying the export as the first thing after a bootup and restarting ID, before you do any other tasks that would require memory.
Thank you for your reply. I did know about the rotated view not transating in the PDF. I was wondering though if it affected the speed of the PDF creating...undoing the rotation.
I was under a time crunch to send off a proof, so after finally force quitting ID, I saved each spread as a separate PDF and then compiled them into a multi-page PDF. It all went without a hiccup. Possibly if I had restarted my computer, opened ID and prepared the multi-pg PDF at that point, as suggested below, then it may have worked. I will be trying that at some point as I will have more comps to prepare as the project proceeds.