Mac OS X 10.5’s Quick Look is a great way to get a preview of nearly any document without opening the application that created that document. Just highlight the document and press the Space Bar. Quick Look is especially useful for PDFs and images. As you’re probably aware, you can page through PDFs in Quick Look mode by using your scroll wheel (or two-finger scrolling on a trackpad). What you may not have known, however, is that both PDFs and image files are can be zoomed within the Quick Look window.
To zoom in on either a PDF or an image, you need to make sure the Quick Look window has focus, so click inside it first. To zoom PDFs, press Command-Equals (=) (or if it’s easier to think of it this way, Command-Plus [+], provided you don’t hit the shift key). To zoom out, press Command-Minus (-). The range of zoom provided for PDFs is truly amazing—and to some degree, completely useless. For example, Quick Look a PDF, and then press and hold the zoom out keys—you can make the entire document appear no larger than a single pixel. Going the other direction, a simple period can fill the screen. I really can’t think of a practical need for this amount of zoom, but it is impressive. (I’m not aware, however, of any quick way to return to 100-percent zoom without closing and reopening the Quick Look window.)
Images, confusingly, use a different method of zooming—and the range of zoom isn’t anywhere near that of a PDF (which makes sense, as PDFs are scalable without distortion, while images are not). To zoom in on an image (again, make sure the Quick Look window has focus by clicking inside it first), hold down Option and click on the image. To zoom out, press Shift-Option and click.
With both PDFs and images, once zoomed in, you can move the image around by using your scroll wheel, trackpad scrolling, or the good old fashioned drag thumbs in the scroll bars.
The more I use Quick Look, the more I like it—especially when it’s full of useful little features such as these.