One of the most popular file formats shared and distributed even before the days of the internet is the Adobe PDF file format. PDF is very popular because it is retains the same document look across all the applications, operating systems and printers. So if you create a PDF document it is going to look exactly the same to everyone who views it anywhere in the world using any application on any system. Even though PDF documents are very popular, they are a little harder to edit. If you want to edit the PDF documents then generally you are expected to pay for commercial software from Adobe.
But if you have to just extract a few images from the PDF documents, buying an expensive commercial software is just an overkill. You can instead use a freeware called PdfTrick that can extract the images from any of the PDF documents. The PdfTrick software is designed using the Oracle Java, so you should have the Java Runtime Environment installed on your machine to run it. But being a Java based software, PdfTrick is cross-platform , i.e., it can be run in Windows as well as Mac. The PdfTrick web site does not specifically give any download links for the Linux users, but they provide the source code and Linux users are free to modify/ compile it for themselves.
You can launch the PdfTrick software and then drag-n-drop PDF document on the PdfTrick window. It will show all the pages inside the PDF document on the left side. You have to first select the PDF page that you want to extract the images from, and then select the images that you want to extract. After this, you can click on Get Img button and it will extract those images to a folder of your choice.
PdfTrick is great for those PDF documents that have full pages made of images only. You can use PdfTrick to extract these images and later edit them using your favorite image editing programs.
You can download PdfTrick from http://www.pdftrick.org/.