ubuntu convert PDF to a image file

Q. A friend showed me how to extract images from a pdf file using pdfimages utility. But I'd like to convert my PDF file to image file. How do I convert a PDF to an image file using a command line option?

A. You need to use convert command from imagemagick - image manipulation set of programs.

The convert program is a member of the ImageMagick suite of tools. Use it to convert between image formats as well as resize an image, blur, crop, despeckle, dither, draw on, flip, join, re-sample, and much more. This is also useful if you do not have PDF reader installed (Gnome and KDE does have in built PDF reader) or required for your webbased project.

Type the following command to convert foo.pdf to foo.png (foo1.png, foo2.png.. etc if you have multiple pages in a pdf file):
$ convert foo.pdf foo.png

You can specify a different file type by changing the file extension of the second file, type:
$ convert foo.pdf foo.jpg

copy paste from
http://www.cyberciti.biz/faq/howto-convert-a-pdf-file-to-an-image/