PDF stands for Portable Document Format. The 'pdf' format is a way publishing files so that anyone using the World Wide Web can download them for viewing and printing.
In order to download a file saved in the .pdf format from this, or any other, website you just click on the link supplied (e.g. [download...]). However you must already have a copy of Adobe Reader or a suitable browser plugin installed on your PC/smartphone.
If you need Adobe Reader for your PC or Mac, you can get it free here [Get Adobe Reader...]