That is how I convert a bunch of jpg files to pdf

createPdfFiles.sh

#!/bin/bash

START_TIME=$(date +%s)
echo
echo "Starting..."
echo

for dirName in */
do
  ( cd $dirName && echo "Generating pdf version of ${dirName%/}" && convert *.jpg ${dirName%/}.pdf )
done

echo
echo "Making result zip file..."
find . -iname "*.pdf" -print | zip documentsInPdfFormat.zip -@

echo
echo "Clearing the unnessery pdf files..."
find . -type f -iname "*.pdf" -exec rm -rf {} \;

END_TIME=$(date +%s)
DIFF=$(( $END_TIME - $START_TIME ))

echo
echo "That was it :)"
echo "It took just $DIFF seconds"
echo