I have a PDF file created by root which ImageMagic cannot convert to a .png file. If I do

convert img.pdf img.png

it works on my mac, but under RH7.4 the program goes into an infinite loop eating 100% CPU.

I attached the img.pdf, but compressed it to img.pdf.gz, otherwise I cannot post here.

Can anyone figure out why ImageMagick won't convert that file?