In this video from SocialMacbook he shows how to merge separate PDF files into one. There is a free way to do it. It will work on Mac and PC. Go to MergePDF. There is a link in the description. Here you can upload your PDF files you want joined together. Click pick files and select the files one at a time that you want merged together. You can only upload files 5 MB less each. It will tell you the size. Now you can click Merge PDF. It will say please wait, and then a box comes up where you can open or save it. Save it to your desktop and now you have merged your separate PDF files into one PDF file.