[EXT] Embedded fonts

[Karl Berry]

      ps2pdf -dPDFSETTINGS=/prepress inputfile.pdf outputfile.pdf

Agreed that is the most important -d for gs :).

For the record, here are all the options I use with ps2pdf for TUGboat
(well, I run gs directly). Most of them do not matter for most
documents, but they've all been necessary at one time or another. 

gs -q -dNOPAUSE -dBATCH \
  -sDEVICE=pdfwrite \
  -sOutputFile="$outfile" \
  -r1200 \
  -dPDFSETTINGS=/prepress \
  -dAutoRotatePages=/None \
  -dCompressFonts=true \
  -dDetectDuplicateImages \
  -dPrinted=false \
  -f "$infile"

The first couple lines are almost replicating what ps2pdf[wr] does, but
I needed full control.

-r1200 is to avoid rendering on a tiny canvas, which can trip
  heuristics of complicated fonts, as (relating to a Hans font) in:
  https://bugs.ghostscript.com/show_bug.cgi?id=701753 

-dPDFSETTINGS=/prepress works so far to ensure embedded fonts.

-dAutoRotatePages since no, we do not want pages randomly rotated.

-dCompressFonts seems not to hurt, and can save notable space.

-dDetectDuplicateImages similarly.

-dPrinted=false is to preserve internal links within the pdf,
  notably for the cover/cover3 in our tb*complete.pdf:
  https://tex.stackexchange.com/questions/456896