If that doesn't work, you might also want to try converting from PDF to Postscript and back to PDF (or just make your JPG from the PS file directly.
If you don't have the packages installed already, use (for RedHat/CentOS):
$ yum install xpdf-utils
$ yum install ghostscript
Then run this
$ pdftops source.pdf convert.ps
$ ps2pdf convert.ps newfile.pdf