I suppose you mean that it's in PDF format, typically opened with Adobe Reader, formerly Adobe Acrobat Reader.
The good way is to install Ghostscript, the Open Source version of Postscript, and its viewer, GSView. This costs exactly $0. With GSView, you may then save the images as JPEG documents.
The other way to do it involves opening the PDF file in Reader and using the Snapshot tool. This will dump an image to the clipboard. You may then paste the image into Paint.NET, Photoshop, or even Microsoft Paint if you so choose. After that, save it.
This is all assuming that you're running Windows. If you're on Mac OS X, just open the files in Preview and use File > Save As. You may select nearly any graphic format there.
I hope this helps! Also please post technical questions in the appropriate Technical Support section 🙂