For whatever reasons if you need to take screenshots of every single page of a pdf file, you would probably want to automate this process. There are some online services, but I needed to do this for work. It turns out in osx there is an easy way to accomplish this with Automator. I am no expert of it, but here is a little workflow I setup to do just that. So if you have a pdf with 30 pages, you will end up with 30 single page pdfs and 30 jpgs. Cheers! ;)