re: "PDF displaced Postscript."
Not exactly. A PDF is generated from PostScript, as noted in the article:
"A PDF file is a static representation of the result of executing the PostScript file on a single occasion."
A PDF is a more compact version of a PostScript file - we could call it compiled PostScript, to use a term many on this site are familiar with. Just as a compiler has many output options, distilling PostScript can result in many different file sizes and levels of quality. (Check out the Distiller output settings.)