Not "for printers" per se. What it was designed for was to accurately represent a printed page in electronic form. So the innards of a PDF look more like "ins

Not "for printers" per se. What it was designed for was to accurately represent a printed page in electronic form. So the innards of a PDF look more like "instructions" for a virtual printer telling it where to position "font glyphs" on a "virtual sheet of paper". It's use as an almost universal "printer format" for applying toner/ink to paper came much later.