Quark needs to use postscript as an interim format to create a PDF (I believe this is still the same with v9, but have only used up to v8.5).
Quark 4 and 5 both have Export to PDF commands but you have to have Acrobat Distiller installed and set Quark's Preferences so that it knows where Distiller is installed, Quark would background generate postscript and pass this through Distiller (at the Distiller Settings you last used) to create a PDF and this would all have to happen under OS9 or Classic. I can't remember with Classic but pre OSX you would have to install and set up a Postscript Printer in the Chooser, LaserWriter8.3.4 or AdobePS8.8.0 were favourites.
Quark5 and Distiller 5 would work pretty nicely under OS9, again I'm fuzzy on Distiller 3 and 4 its such a long time ago but I know I had both Q4.11 and Q5.01 with Distiller4.0.5 running on OS9.0.4, I just can't remember what did and didn't work.
Later versions of Quark internally use JAWS to Export to PDF but there is still the postscript interim stage.
Re the advantages of PDF Trim box info getting in the pdf, this only used to happen because Distiller would recognize the pattern of earlier quarks crop marks, earlier versions of Distiller would need a start-up plug-in from someone like Creo to do this.