unshitPDF.sh

#!/bin/bash

if [ "$1" = "--help" -o "$1" = "-h" -o '(' $# -ne 1 -a $# -ne 3 ')' ]; then
	cat <<- EOF
		This script rearranges PDFs that have multiple pages printed on the
		same sheet, like this:
		_________
		| 1 | 2 |
		---------
		| 3 | 4 | page 1
		---------
		| 5 | 6 |
		---------
		                                                                    
		into a single-page single-sheet pdf, like this:
		_____
		| 1 | page 1
		-----
		-----
		| 2 | page 2
		-----
		  .
		  .
		
		it uses the 'mutool' program to split pages.
		it uses the 'qpdf' program to reorder the pages generated by mutool
		                                                                    
		On archlinux mutool is in the mupdf-tools package
		EOF
	echo
	echo USAGE: $0 pdf_file [columns_num rows_num]
	echo default value for columns and rows per page is 2
	exit 1
fi

tmpd="$(mktemp -d mutool.XXXXXX --tmpdir)"

# reading parameters
pdfin="$1"
cols="$2"
[ -z "$cols" ] && cols=2
rows="$3"
[ -z "$rows" ] && rows=2

# splits pages into vertical pieces
if [ $rows -ne 1 ]; then
	mutool poster -x "$rows" "$pdfin" "$tmpd/h.pdf"
else
	mv "$pdfin" "$tmpd/h.pdf"
fi
cd "$tmpd"

# splits pages into horizontal pieces
if [ "$cols" -gt 1 ]; then
	# mutool splits columns in reverse order for some obscure reason
	mutool poster -y "$cols" h.pdf v.pdf
	npages=$(mutool info v.pdf | egrep '^Pages: ' | cut -d ' ' -f 2)
	echo $npages pages to elaborate
	let r=0
	pages=''
	while [ $npages -gt 0 ]; do
		let c=$cols
		while [ $c -gt 0 ]; do
			pages="$pages,$((($r*$cols)+$c))"
			let c--
			let npages--
		done
		let r++
	done
	#echo ${pages:1}
	qpdf --empty --pages v.pdf ${pages:1} -- final.pdf
else
	mv h.pdf final.pdf
fi

cd - > /dev/null
mv "$tmpd/final.pdf" "$pdfin"
rm -r "$tmpd"