This one might be more widely known than other little tricks that I’ve shown of-late but here goes. In OS X you can PDF anything that you can print. Just go File>Print and select “Save as PDF” at the very bottom left of that window.
The fun part comes from the fact that you can then open any PDF in Photoshop as super high-resolution raster images. This is how all those meta/media/material artists can make humongo-sized printouts of their spiffy web designs.