As per the SysAdmin Diary at (…feisty/):

  1. Add the Medibuntu repositories as per instructions at At the command line:
    echo “deb feisty free non-free” | sudo tee -a /etc/apt/sources.list
    wget -q -O- | sudo apt-key add – && sudo apt-get update
  2. Add the acroread, acroread-plugins, and mozilla-acroread packages
    sudo apt-get install acroread acroread-plugins mozilla-acroread
  3. Restart Firefox