Acrobat Reader used to be available from Ubuntu Partner repository, but it is not available anymore in Ubuntu 12.10 Quantal Quetzal!
So you have to download the .deb package from adobe.com and install it:
However, if you have a 64bit system, do not forget to install also these packages:
sudo apt-get install libxml2:i386 ia32-libs
Otherwise, acroread will fail
acroread: error while loading shared libraries: libxml2.so.2: cannot open shared object file: No such file or directory