Some PDF Images Extract
Some PDF Images Extract is a free Web site that can render PDF documents into JPEG, TIFF, or PNG images. The site works by having you upload your PDF file, then, each page is rendered into an image of the dimensions and format you specify. The site is quite limited: you can only specify a rendering DPI, not pixel dimensions, and, despite the name, the site can't actually extract images from PDF files, it can only render pages. So, if you save to JPG format, you will lose quality. I used to use this site before I found out about the much more impressive XPDF tools which I now use instead.