How do I change a PDF file into a jpeg?

I have this picture in a pdf but I need it to a jpeg. I can't download anything because I'm on a school computer. Anyone know own that dosen't need download. Does photoshop work the Libray computers have that?How do I change a PDF file into a jpeg?
you can import your pdf document into photoshop then convert it into image,as to create pdf simpo pdf creator is the best choice.How do I change a PDF file into a jpeg?
Shift - Print Screen

It usually is a key between the main keyboard and the ten key pad.

Then Start - Program - Accessories - Paint and paste it and crop it and cut it and paste it into a new file. You might want to zoom in on the picture before taking screen shot.
if the PC doesnt have acrobat full version, print screen maybe your only option aside from bringing along a program on a USB flash drive