If you don't have installed program for editing PDF documents on your computer, then you can use web application PDFescape which allows you to edit your documents in your browser.
You can add multiple desktops to the Mac OS X Mountain Lion by using Mission Control, formerly known as Spaces. Can be really useful if you are a busy multi-tasker.
Awesome guys at Visual.ly just released a a free online tool that can visualize Google Analytics stats into a great looking report in a form of infographic in a matter of basically only a click.