script.sh

#!/bin/bash

# Install ghostscript.
# Assume A and B have the same amount of files.
# Assume file in A are named `testo_1`, and files in B are named `disegno_1`.

END=`ls A/*.pdf | wc -l`

echo "merging..."

for (( c=1; c<=$END; c++ ))
do
        gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=C/report_$c.pdf A/testo_$c.pdf B/disegno_$c.pdf
done

echo "done"