Bash script to merge multiple (possibly protected) PDFs

sort-and-unrestrict-and-merge-pdfs.sh

#!/bin/bash

# execute in a directory with the respective PDF files only

echo "Execute this script only if"
echo " 1. this directory contains only the PDF files you want to merge"
echo " 2. you have no problem that this script will rename them"
echo " 3. you downloaded them in their linear order (first chapter first; this tool is based on the creation date)"

read -rsp $'Press enter to continue or CRTL-C to abort...\n'

#qmv -t -r --format destination-only
for f in *.pdf
do
  mv -n "$f" "$(date -r "$f" +"%Y%m%d_%H%M%S_$f")"
done

for i in *.pdf; do
  echo
  pdftk "$i" output "$i.unrestricted.pdf" allow AllFeatures
  echo
  #qpdf --decrypt "$i" "_$i"
done

pdftk *.unrestricted.pdf cat output output.pdf