JSTOR remove PDF download information (your IP and the date)

jstor_unmetadata.bash

#!/bin/bash
# RIP Aaron Swartz, killed by corporate greed. (Not JSTOR itself, they are a charity;
#                                               I mean the publishers they must contract with
#                                               to offer the limited public service that they do.)
#
# “There is no justice in following unjust laws.
#  It’s time to come into the light and, in the grand tradition of civil disobedience,
#  declare our opposition to this private theft of public culture.” ~ Aaron Swartz 
#
# Requires:
# * pdftk (Java edition)
# * mat2 (Metadata anonymisation toolkit 2 [by Tails project])
# * qpdf (https://qpdf.readthedocs.io [by Jay Berkenbilt])
#
# Usage:
#   source jstor_unmetadata.bash # perhaps add me to $HOME/.bashrc
#   jstor_unmetadata "$INPUT" "$OUTPUT"

mktemp_eval () 
{ 
    T="${T:-"`mktemp`.pdf"}"
    cat /dev/stdin > "$T"
    eval "$@" && cat "$T" && rm "$T"
    return 0
}
__jstor_unmetadata_inner () 
{
    PAT1='This content downloaded from'
    PAT2='on .*[\000]'
    mapfile -d -t JSTOR_AWK /dev/stdin << '    EOF'
        {s=$0;}
        function DOIT(s){
            var="";
            for (i=0; i<length(s); i++) { var=var"\0"; }
            gsub(".*", var, s);
            return s;
        }
        $0~PAT1{s=DOIT($0)}
        $0~PAT2{s=DOIT($0)}
        {print s}
    EOF
    gawk -v PAT1="$PAT1" -v PAT2="$PAT2" "$JSTOR_AWK" < /dev/stdin
    return 0
}
jstor_unmetadata() {
    ( ( mktemp_eval 'pdftk "$T" output - uncompress' | __jstor_unmetadata_inner ) | mktemp_eval 'mat2 -L --inplace "$T"' | mktemp_eval 'qpdf "$T" --linearize -' ) < "$1" > "$2"
}

NB: GitHub is not as good at Bash as I am. ' EOF' is perfectly valid, their syntax highlighter is wrong, this script does run.