add_signs_to_pdf.sh

for i in `seq 1 15`; 
do 
 pdftk documento.pdf cat "$i" output "$i.pdf"; 
done

for i in `seq 1 15`; 
do 
  pdftoppm $i.pdf > $i.ppm; 
done

mkdir signed

for i in `seq 1 15`; 
do 
  convert "$i.ppm" ~/Documents/me/firma.png -density 600 -quality 100  -gravity southeast -geometry +20+20 -composite signed/"$i"_signed.jpg; 
done

pdftk signed/*.pdf cat output documento_firmato.pdf