can i download ibooks on a Mac Pro ?

If you mean the books then yes, but unless they are free or from a publisher such as O'Reilly (who don't put digital rights management on their books) then you won't be able to read them on your Mac.

With OS X Mavericks later in the year that will change, that has an iBooks app for Macs in it : http://www.apple.com/osx/preview/#ibooks