Overlay image and text on a PDF with imagemagick and ghostscript

gs.sh

#!/bin/sh

set -eu

srcfile1="$1"
srcfile2="out.pdf"
out="${srcfile1%\.*}-signed.${srcfile1##*\.}"

gs -dBATCH -dNOPAUSE -dQUIET -sDEVICE=pdfwrite \
  -dLastPage=1 -sOutputFile="$out" "$srcfile1" "$srcfile2"

sign-pdf.sh

#!/bin/sh

set -eu

srcfile="$1"
pg="1"  # 0-based index
size_img="24%"
sigfile="signature.png"
pnt="12"
txt="  $(date '+%d-%h-%y')  "  # spaces for bigger bounding box
geom_img="+600+880"
geom_txt="+550+950"
outfile="out.pdf"

convert \
  -density "${dens:-400}" \
  "$srcfile[$pg]" \( \
    -resize "$size_img" \
    -gravity "${grav_img:-northwest}" \
    -geometry "$geom_img" \
    "$sigfile" \) \
  -compose over -composite \
  -gravity "${grav_txt:-northeast}" \
  -box "${bounding:-white}" \
  -pointsize "$pnt" \
  -draw "text $geom_txt '$txt'" \
  "$outfile"