> Well, they are embedded in the PDF as a Type 1 font. That support can in principle be removed (e.g., if your font rendering depends on a library shared with other software that drops Type 1 support), although indeed that would not be in the spirit of PDF (and go against what is now an ISO standard).
Type 1 fonts are a subset of Postscript sufficient to describe glyph outlines, plus hinting and font specific metadata.
PDFs are a larger subset of Postscript that keeps more features but still strips it down from a programming language to a document description language while adding a stricter structure, embedding of files, and other features relevant to its use as digital paper.
The Venn diagram of PostScript, PDF, and Type 1 fonts has a LOT of overlap. Any useful Postscript or PDF viewer inherently has to support everything about Type 1 fonts other than hinting, and hinting only matters at sizes where subpixels matter.
Type 1 fonts are a subset of Postscript sufficient to describe glyph outlines, plus hinting and font specific metadata.
PDFs are a larger subset of Postscript that keeps more features but still strips it down from a programming language to a document description language while adding a stricter structure, embedding of files, and other features relevant to its use as digital paper.
The Venn diagram of PostScript, PDF, and Type 1 fonts has a LOT of overlap. Any useful Postscript or PDF viewer inherently has to support everything about Type 1 fonts other than hinting, and hinting only matters at sizes where subpixels matter.