To bring my readers the Fluids book I had to merge multiple PDFs into a single document. For example, the Hyponatremia chapter exists on my hard drive as 4 separate pagemaker files. These can be converted to four separate PDFs. To put them together is trivial in Mac OS X. No Acrobat Pro or other nonsence needed:
And from with a little more context from Mac OS X Hints
Use Preview to open up the two PDFs you would like to merge. Choose View » Show Sidebar (or click the Sidebar button). Make sure both PDFs are visible on the screen at the same time. When the Sidebar pops out, you will see a graphical representation of the pages in your PDF document. Simply drag the page, or pages (use Comand to select multiple pages) from the Sidebar of one PDF to the Sidebar of another. You have now merged pages from two separate PDF documents.
So easy. So simple. So elegant.