You should not have any problem dealing with the download on a PC. On the ipad or iphone you need some additional software like 'GoodReader'.
Basically your need something being able to open a zip file and read a pdf. GoodReader does it for you:
Go to to itunes for GoodReader.
This app is not free.
A good and free unzip program might be winzip.
Go to itunes for winzip.
You do need a pdf reader next to the unzip program in the latter case.