Use the following tiny script to make PDFs look like they have been scanned.

scan.sh

#!/bin/sh

# Help message
show_help() {
  echo
  echo "Convert PDFs to make them look like they have been scanned"
  echo "Example: $0 file.pdf"
}

# Check if the provided argument is not empty
if [ -z "$1" ]; then
  echo "Error: Argument cannot be empty."
  show_help
  exit 1
fi

# Assign argument to variable
ORIGINAL_PDF=$1

# Generate the scanned PDF filename by appending '_scanned' to the original filename
SCANNED_PDF="${ORIGINAL_PDF%.pdf}_scanned.pdf"

# Random rotation value
ROTATION=$(shuf -n 1 -e '-' '')$(shuf -n 1 -e $(seq 0.05 .5))

# Convert the PDF
convert -density 150 "$ORIGINAL_PDF" \
  -linear-stretch '1.5%x2%' \
  -rotate "${ROTATION}" \
  -attenuate '0.01' \
  +noise Multiplicative \
  -colorspace 'gray' "$SCANNED_PDF"