Put a stamp on the last page of a PDF document using PDFTK

stamp-last-page.sh

#!/bin/bash

if [ "$1" == "" -o "$2" == "" -o "$3" == "" -o "$4" != "" -o "$1" == "-h" -o "$1" == "--help" ]; then
	echo "Puts a stamp (as PDF file) onto the last page of the input" >&2
	echo "file using PDFTK". >&2
	echo "" >&2
	echo "Usage: $0 INPUT.pdf STAMP.pdf OUTPUT.pdf" >&2
	exit 1
fi

tmpfile1="$(mktemp --suffix=.pdf)"
tmpfile2="$(mktemp --suffix=.pdf)"

cleanup() {
	test -e "$tmpfile1" && rm "$tmpfile1"
	test -e "$tmpfile2" && rm "$tmpfile2"
}

die() {
	echo "$@" >&2
	cleanup
	kill $$
	exit 1
}

addStamp() {
	pdftk "$1" stamp "$2" output "$3" || die "Failed to add stamp"
}

case "$(pdftk "$1" dump_data | grep -oP '(?<=NumberOfPages: ).*')" in
	0)
		die "Cannot handle empty document"
	;;
	1)
		addStamp "$1" "$2" "$3"
	;;
	*)
		# Extract last page and put stamp on it
		pdftk "$1" cat end output "$tmpfile1" || die "Failed to extract last page"
		addStamp "$tmpfile1" "$2" "$tmpfile2"

		# Extract all but last page
		pdftk "$1" cat 1-r2 output "$tmpfile1" || die "Failed to extract page range"

		# Merge both
		pdftk "$tmpfile1" "$tmpfile2" cat output "$3" || die "Failed to merge pages"
	;;
esac

cleanup