This script inputs a pdf file and outputs a pdf file that is in booklet format. You will then be able to print the output file using duplex (both sides of paper) and 2 pages per side. The script is also capable of printing multiple signatures.

booklet.sh

#!/bin/bash
# booklet.sh - This script inputs a pdf file and outputs a pdf file that is in booklet
#              format.  You will then be able to print the output file using duplex
#              (both sides of paper) and 2 pages per side.  The end result is a printed
#              document that can be stapled in the middle and folded so that it may be 
#              viewed like a book.  The script is also capable of printing multiple
#              signatures.
#
#              This script is licensed under the GPL license v3. 
#              See https://www.gnu.org/copyleft/gpl.html for more information.
#              
# Basic Usage: sh booklet.sh file.pdf
#
# Note: you can also specify the crop with a second argv
# i.e., sh booklet.sh file.pdf 10
#
# Note: Again, this script assumes that you are going to print 
#       using duplex, 2 pages per side.


# Check for empty input and print Usage if empty.
case $1 in 
	"")
	    echo
	    echo "####Instructions####"
	    echo "# booklet.sh - A script that formats a pdf into a booklet."
	    echo "Usage: sh $0 file.pdf"
	    echo "# Note: you can also specify the crop with a second argv"
	    echo "sh $0 file.pdf 10"
	    echo "###################"
	    echo
	    exit

	;;
	*)
	file=$1
	case $2 in 
		"") #if no crop argv default is 10.
		cropin=10
		;;
		*)
		cropin=$2
		;;
	esac
	;;

esac


#get number of pages of $file
pagenum=$(pdftk $file data_dump output |grep -i Num |awk '{print $2}')

# divisorslist n will output the divisors of n.
# $1=ssinglesigpagenum
function divisorlist() {

local divisors
local x=$1
local i=2 # possible divisor
local j=2
local k=1
local n=$(expr $x / 2) # top limit for divisor

divisors[1]=1

while [ $i -le $n ]
do
	let k=$x%$i # residual
	if [ $k -eq 0 ]
	then
		divisors[$j]=$i
		let j=$j+1
	fi	
	let i=$i+1
done
divisors[$j+1]=$1
echo "${divisors[@]}"
} 

# convert file n m will convert file to a booklet
# of with signature of length n and crop of size m.
# The only function that actually does anything.
# $1=$file $2=$siglength $3=crop
function convert() {

local files=$1
local siglength=$2
local crop=$3
local filebase=$(basename $1 .pdf)

pdfcrop --margins $crop $files ${filebase}-crop.pdf
pdf2ps ${filebase}-crop.pdf
psbook -s $siglength ${filebase}-crop.ps >${filebase}-booklet.ps
rm -f ${filebase}-crop.pdf ${filebase}-booklet-crop.ps

echo "* Converting back to pdf ..."

ps2pdf ${filebase}-booklet.ps
rm -f ${filebase}-booklet.ps ${filebase}-crop.ps

}

# pagenum0mod4 file pagenum outputs page number that is 0mod4
# $1=$file $2=$pagenum 
function pagenum0mod4() {

local files=$1
local pagenum=$2
local diffmod=$(($pagenum % 4))
local newpagenum=$pagenum
local pagenumadd=$((4 - $diffmod))

if [ "$diffmod" = 0 ]
then
  newpagenum=$pagenum
else
  newpagenum=$(($pagenum + $pagenumadd))
fi

echo $newpagenum
}

# where the magic happens. 
# $1=$file $2=$newpagenum $3=cropin
function userinterface() {

local files=$1
local newpagenum=$2
local crop=$3
local switch=0
local singlesigpagenum=$(($newpagenum / 4))
local signaturechoices=($(divisorlist $singlesigpagenum))

# Ask for length of each signature 
# and do stupidity check on input.
while [ $switch = 0 ]
do

	echo
	echo "Question: How many signature do you want? (If you do not know, 1 is recommended) 1 signature requires $singlesigpagenum pages for this document."
	echo "[Choices are ${signaturechoices[@]}] or Ctrl+c to exit:" 
	read signum

	for j in ${signaturechoices[@]}; do
		case $signum in 
			$j)
				switch=1;
				break;
				;;
			*)
			;;
		esac

	done

done

#siglength is length of each signature
local siglength=$(($newpagenum / $signum))

echo
echo "*Creating $signum signatures $siglength pages long..."
convert $file $siglength $crop
}


####################################
# main() - lets run this shit.  
newpagenum=$(pagenum0mod4 $file $pagenum)

echo
echo -e "There are $pagenum pages in:"
echo "- $file"

echo "...."
echo "New document will have $newpagenum pages and will be cropped $cropin."

userinterface $file $(pagenum0mod4 $file $pagenum) $cropin
echo