Here are two ways to convert an Apple Pages document to PDF. Neither is better than the other. Select Export to from the File menu and choose PDF. Print the document and instead of hitting the Print button select an option from the PDF pop down menu in the lower left corner of the Print dialog box. The last option is particularly useful if you want to mail someone the PDF or save it directly to a specific location (as indicated by the options).
When you print a book it goes into two folders; the book, and the cover.