I've been getting this error for a while on my production server (Ubuntu running ImageMagick, Rmagick, etc).
From Googling around it seems to be not finding the right fonts to use, and this needs to be set correctly in
sudo nano /usr/lib/ImageMagick-6.3.7/config/type-ghostscript.xml
When I open up this file it lists a bunch of fonts in this directory
/usr/share/fonts/type1/gsfonts/
They all exist. I've tried changing the owner and permissions on those fonts. Doesn't seem to help.
Has anyone encountered this and been able to fix it? Thanks!