PDFHammer is a great tool that enable you to edit PDF files online. No need to download anything to your computer, just upload a PDF document to the site and edit it inside your browser. Once you start, you will be able to upload one or more PDF files into your project, arrange the pages in any order you wish, and delete any pages you don’t want.
At the end of your project you’ll be able to export the final PDF.
No registration BTW.. just a simple, useful tool.
I found this lovely PDF file on Docstoc.