Program locking up when working with combined files that get large. Large meaning 50 mb or more, I have beeen breaking my book up in sections because Adobe will not process, anybody familiar with this problem with adobe, it's frustrating!
It's normal to work with files of hundreds of megabytes and thousands of pages. What specifically are you doing that's slow, and - I'm not sure I see - why are you combining at all? Most often a book is just prepared in Word or InDesign or whatever as a single PDF.