I got the idea from an earlier prank, a printout of a fake WebMD page. A friend had been garggling with hydrogen peroxide and accidentally swallowed some and asked me if that was dangerous. The page contents started out real, but I added increasingly severe and deadly consequences. As she read the two page report, her eyes got as big as pancakes! But as to not make her actually believe she was going to die, the last ones on the list were quite outlandish, revealing the joke. "Oh, you guys! You got me so good!" she said.
Step 1: Photoshop It
If you don't have Photoshop, you can get a free 30 day demo from the Adobe website or use another graphics program.
Step 2: Write It
You can type it up in wordpad or any editor and paste it in a text layer in Photoshop. If you want it to look real, don't use too many font types.