I attempted to open a reference manual in PDF format today on Ubuntu 12.04 LTS (Precie Pangolin) and was sorely disappointed to find that the default application, Evince Document Viewer, had no search or find feature. Unforgivable. Here is how you can install Adobe Reader and make it your default PDF viewer – just enter the following commands into your command line shell:
sudo apt-add-repository "deb http://archive.canonical.com/ $(lsb_release -sc) partner"
sudo apt-get update
sudo apt-get install acroread
During the install process Adobe Reader will ask if you want to make it the default for PDF files.