pdf.js is a new JavaScript library by Marak Squires and Matthew Bergman that allows you to create simple PDF files directly in a client's Web browser or, if you choose, with the node.js server-side JavaScript implementation.

Browser-generated PDFs are served using data-based URIs, such as this one (hover over the link to see the long URL). A page has been set up where you can create some on the fly in your browser right now.