1. This is a simple single line of command that u write at the terminal to install a third party app that will install a pdf printer in ur Ubuntu System.
sudo apt-get install cups-pdf
2. This will be generally handy when u need to print your documents that are ready to print but u don't have a printer installed....actually create a virtual PDF printer on your ubuntu PC that lets you convert all your documents/images/anything into PDFs that you can subsequently send to print as and when u have the facility to print.
3. Thanks http://ubuntuportal.com