How to change font size in Ubuntu 12.04
Unity, a new Ubuntu’s default desktop shell (from 11.04) has a reputation of being not very customizable. Canonical purpose to simplify Linux GUI and made it more accessible limits more experienced users in some ways and force them to undertake additional post installation steps.
For example, after default installation of Ubuntu 12.04 LTS you can't even change default font size for menus, toolbars, icons and windows. In my opinion, the default Ubuntu font size (11-13px) is too large for laptops with 1366x768 screen resolution. That's why I always change it to 10px on my laptop.
If you want to change the font to the preferable size, first you have to install gnome tweak tool.
Open terminal window (ctrl+alt+t) and execute following command:
sudo apt-get install gnome-tweak-tool
then click on Dash Home or press SuperKey. Type "advanced settings" and hit Enter key.
You should see such window:
Next choose Fonts from the list.
Now you are able to change default, document, monospace and window title font size.