Wrapper over the gs operation to stitch PDFs. Save as a script on your local, or slightly modify and you can throw it in a function.

all_pdf_files_to_combined_pdf.sh

#!/usr/bin/env bash

set -e

if [[ -z "$(which gs)" ]]; then
    printf 'Ghostscript (gs) is not installed, please install it to continue.\n\tExample: `brew install gs`\n'
    exit 1
fi

usage="Usage:\n\tall_pdf_files_to_combined_pdf RESULTING_PDF_FILE_NAME pdf1 pdf2 ...\n"

output_file_name="${1}"

if [[ -z "${@}" ]]; then    
    printf "${usage}\n"
    exit 1
fi

shift

if [[ -z "${output_file_name}" ]] || [[ -z "${@}" ]]; then    
    printf "${usage}\n"
    exit 1
fi


printf "Going to combine all files in this directory into a single PDF.\n\n"
printf "Output file name: ${output_file_name}\n"
printf "Files to append together:\n"

args_str=""

for arg in "${@}"; do
    args_str="${args_str}\"${arg}\" "
    printf "\t${arg}\n"
done

printf "\n"

command_str="gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=\"${output_file_name}\" ${args_str}"

printf "\nResulting command to be run:\n\t${command_str}\n"

printf "${command_str}" | sh

printf "\nDone."