PDF documents are most widely used because one cannot change the content in it. One cannot extract images or text directly from PDF files although you can use copy and paste technique to perform this task. You need to have full version of Adobe Acrobat to extract images and text in various format. But this is not possible for all of us there are several free tools available using which you can extract images easily without any effort.
Here are some free tools which help you to extract images from PDF files and save them in various different formats. Some of these applications can also extract text.