In /usr/bin/pdf2ps line 7:
gs="`dirname \"$0\"`/$GS_EXECUTABLE"
    ^--------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
gs="$(dirname \"$0\")/$GS_EXECUTABLE"


In /usr/bin/pdf2ps line 28:
    outfile=`basename "$1" \.pdf`.ps
            ^-------------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
    outfile=$(basename "$1" \.pdf).ps


In /usr/bin/pdf2ps line 30:
    echo "Usage: `basename \"$0\"` [-dASCII85EncodePages=false] [-dLanguageLevel=1|2|3] input.pdf [output.ps]" 1>&2
                 ^---------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean: 
    echo "Usage: $(basename \"$0\") [-dASCII85EncodePages=false] [-dLanguageLevel=1|2|3] input.pdf [output.ps]" 1>&2


In /usr/bin/pdf2ps line 37:
exec "$GS_EXECUTABLE" $OPTIONS -q -dNOPAUSE -dBATCH -P- -dSAFER -sDEVICE=ps2write "-sOutputFile=$outfile" $OPTIONS -c save pop -f "$1"
                      ^------^ SC2086: Double quote to prevent globbing and word splitting.
                                                                                                          ^------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
exec "$GS_EXECUTABLE" "$OPTIONS" -q -dNOPAUSE -dBATCH -P- -dSAFER -sDEVICE=ps2write "-sOutputFile=$outfile" "$OPTIONS" -c save pop -f "$1"

For more information:
  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...
  https://www.shellcheck.net/wiki/SC2006 -- Use $(...) notation instead of le...