You can also use Google image search to research a project. Unlike the PDF search, the image search provides a photo of what the project will look like, which is helpful in determining if you want to pursue building it. By doing an image search for how to build a step stool, you will have a ton of options that all lead to woodworking plans of various quality. (The how to part of these is important—otherwise you’ll just get pictures of step stools.)
Google is probably the first place where most people would start searching for woodworking plans, but often the top results can be a mix of articles and how-to pieces that just aren’t detailed enough. Sometimes they’ll link to the plans (like we try to here at Lifehacker), but other times, they’re just showing off a cool project. There are better, more precise ways of finding what you’re looking for.