adobe reader trying to install and getting nowhere

Newbie here. tempted to return this new Mini mac bought 12 days ago.. So used to Window MS from win98 to Xp on my other computers
.wanted to look at a pdf file on a web site.. Hubby said site told him I did not have it. So he downloaded. It will not install. It ask for my password. I do not know it. I dont even remember it. I dont really remember putting in one I am really only one using this new mini mac, Why does it need such??? I downloaded Firefox and installed it just fine. It did not ask for my password
Guess I will have to call someone since I have tried over and over with the Mac disk to reset my password. It wont let me get pass the "password " part to be able to install Adobe reader
Thanks
jean