It's a BIG one

Smaller projects can usually be handled by the small business owner or consumer with a home computer. Once it is decided that a project has multiple pages, it would be a good idea to work with a designer who has had a great deal of experience in this area.
Knowing how to layout the pages so that they fall in a printer's spread (allowing for nonconsecutive pages to be organize in a way so they fall into the correct order) can be overwhelming and potentially costly if the printer has to fix the file if the setup is incorrect.
I know of some printers which ask that pages be saved as separate files just so they know that they can be sure and put them in the proper order.
So, when planning a large project such as a catalog, sit down with the designer and plan out the necessary sections, photo needs and any inserts. It is money well spent and you will have a project that resembles the original intent.