PDF Image Extract
is a free Windows utility that does exactly what the name suggests: it extracts images from PDF files. Sure, you could save pictures one at a time the old fashioned way by hitting print screen and pasting the image into an editor or using a screen capture program. But PDF Image Extract saves you a lot of time if you want to save multiple images because it will save every single image in a PDF file for you. In fact, you can create batch jobs to save images from multiple documents.
The only down side? I'm not kidding when I say PDF Image Extract saves every
image. You'll likely wind up with a folder containing hundreds of images, only a few of which are the ones you were looking for. That's because the program will save all sorts of segments of the original PDF as image files, including the background.