>>I think it's created on-the-fly while .pdf is created, in at least some of the PDF creators. GhostScript actually does exactly that, converts a .ps into a .pdf file, and somewhere in its documents I thing it does say that PDF is sort of a compiled .ps - but then it's been a couple of year since I played with that, so I'm not sure I could find that again.
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>I'll defer to you, but isn't Ghostscript a converter that happens to require a PS printer driver to create a file as a first step?

It converts a .ps file into pretty much any other format. I've tried pdf, jpg, png, tiff, and it does each in any resolution you tell it.

But it doesn't matter how you get the .ps file - I've created mine using Text/Endtext :).

>Ghostscript could probably have been written to take HP-PCL or Kyocera Prescribe as input formats, too.

And who knows, maybe there's a product out there which would do that.

>I don't think PS is a requirement for PDF. For Ghostscript, sure. But not for PDF.

Maybe historically it was, since both .ps and .pdf are Adobe's kids. But over time I'm sure others have found a way to skip that and take printing commands straight into PDF. So I'd agree, it's probably not used now in many cases.