convert .ps/.pdf to .png files

If ImageMagick is installed your OS, we can convert ps/pdf files to .png image files as follows.

convert -density 150 -geometry 100% some-pdf-file.pdf new-name.png

where, -density 150 : resolution
-geometry 100% : resize scale

this is from :
http://kpwu.wordpress.com/2006/01/26/conver-all-ps-to-png-format-by-a-script/