This tutorial will give you the idea on how to merge different files into one single pdf or
documents in order to do this things ,, you have to download this software first
MergePDF 1.8.2
This software will allow you to merge multiple files and the primary purpose of this application is to determined the order of binding the PDF/image files according to their view sorting order in the Finder. The PDF files will merge with the order displayed.
Additionally, MergePDF is also able of creating bookmarks named according to their original file names and thumbnails.
Tutorial on How to merge pdf files
