it really depends on what platform you’re runnung, but for each (XP,OSX,Linux) there are solutions. Google will get you there.
…I dont know if I am interpreting what you want correctly. Do you want to
a.)Strip just the pictures out of a .pdf file and save them as individual jpegs?
OR
b.)Convert the entire pdf file into a single jpeg copy?
Google can lead you to solutions for both, but if you run into trouble it might help to know.