Inspired by Bear Grylls's (of Discovery's Man vs. Wild) "make the most out of your situation" scenarios, I present you with a tutorial for making the most out of Preview.app. While not as powerful as graphics editing powerhouse Adobe Photoshop, Preview can oftentimes get you from Point A to Point B -- and sometimes quicker too.
Like Bear Grylls, you'll need to parachute out of a plane and into the house of a friend who doesn't have Photoshop -- just kidding.
First, a little bit of background. Preview comes pre-installed on Mac OS X, and it's the default image viewer on the system. For PC-to-Mac converts, you could think of it as the Microsoft Paint of OS X; except that it can do a whole lot more. Besides the ability to open a host of image file formats (JPG, BMP, GIF, among them, and even PSD and AI files), Preview can also open PDF files natively. I actually prefer it over Adobe Acrobat for opening PDFs, as I find that they open much quicker using Preview. And like Adobe Reader, Preview contains advanced features, such as annotating.