A PDF file is especially useful when multiple PDF files can be combined into one file. When you combine a couple of PDF files, it is easy to use Preview in Mac (sorry I do not know Windows computers). However, if you want to combine hundreads of files, using Preview is not good choice. Fortunately Mac has a useful program for automation, called Automator. Furthermore, there is a useful blog to explain how to use Automator to combine PDFs. I added one last step to create combined file name (Fig. 1). To do this, click “Rename Finder Items” under “Files & Folders” in Actions column and move it to right panel after “Move Finder Items” step. Amd then change parameters as shown.

Fig. 1. Automator Fig.1