http://www.entropy.ch/blog/Mac+OS+X/2006/10/24/AppleScript-to-merge-MS-Word-Section-PDFs.html
[kirkmc adds: I haven't tried this, but I know the Preview solution does not work all the time. There's some quite complex code in this solution, so it's not just a drag-and-drop operation. Do post in the comments if you get this to work or not.]

