[Therion] Generated PDF compliant to spec?

[Carl Magnuson]

I tried converting my PDF map to a JPG using Ghostscript yesterday.  It seemed to convert properly, though I saw a handful of warnings that there was an "Unknown operator: 'pop'" in the source PDF.  Is Therion producing something which isn't to spec, or producing a newer version PDF that Ghostscript isn't prepared for?  I was using Therion 5.3

Thanks,

Carl