These scripts are handy if you have a collection of PDF's that you would like to combine into one.
Use this script if you only have a small batch of PDF's that you would like to combine, less than 100 for example.
If you have several hundreds or even thousands of PDF's to combine, this is the script to you. Just keep in mind that you are looking at some serious computer resource allocation here. For example, I merged 5 million pages of PDF's from 50,000 files and it was a several hour endeavour.