Here is a Bash script that takes command line arguments for the source PDF files and the output merged PDF file. The script uses Ghostscript (gs) to merge the specified PDF files.

merge-pdfs.sh

#!/bin/bash

# Check if at least two arguments are provided (at least one source and one output)
if [ "$#" -lt 2 ]; then
    echo "Usage: ${0##*/} output.pdf source1.pdf [source2.pdf ... sourceN.pdf]"
    exit 1
fi

# The first argument is the output file
output_file="$1"

# The remaining arguments are the source PDF files
shift # Remove the first argument from the list
source_files="$@"

# Run Ghostscript to merge the PDFs
gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile="$output_file" $source_files

# Check if the merge was successful
if [ $? -eq 0 ]; then
    echo "Merged PDF successfully!"
else
    echo "Error while merging PDFs!"
    exit 1
fi