#!bin/bash
# This script is written for files that are named with the pattern
#pg_0001.pdf, with leading zeros.

a=1 #Sets the starting page. 'Could set with user input.
b=$(($a+1))#Sets the next page equal to one more than the starting page.

Filename="pg_"`printf "%04d" $a`".pdf" # This is the filename of the
#starting page. The printf command is used to format the number with
#up to three leading zeros.

until [ $b == 680 ]; do # This line sets the maximum pages to be
#considered for concatenation.
Filename2="pg_"`printf "%04d" $b`".pdf" # This is the filename of the
#next file to be considered for concatenation to the current file.
x=`pdfgrep -C 0 [0-9]\{7\} $Filename | head -n 1` # pdfgrep with
#option to, -C, capture 0 characters other than the 7 digits in the
#employee ID; this is piped to "head" in order to get just the first
#occurrence.
y=`pdfgrep -C 0 [0-9]\{7\} $Filename2 | head -n 1`

if [ "$x" == "$y" ]; then 
    pdfjoin --rotateoversize 'false' $Filename $Filename2 --outfile $Filename # If the employee ID's are equal, then the pdf files
#are concatenated into a new file, which is given the name of the
#first file that's added to.
    rm $Filename2 # If the file is concatenated to a previous
#file, it is removed.
else
cp $Filename Empl_ID_"$x".pdf # Replace page number name with name
#based on Empl_ID.
#rm $Filename # Uncomment to remove the original file.
Filename=$Filename2 # If no match is found and the file is not
#concatenated, then advance the current origination file, Filename, to
#the name of the non-concatenated/non-matching file.
fi

b=$(($b+1)) # Advance the page number of the next file, Filename2.

done

cp $Filename Empl_ID_"$x".pdf # Finally, when all else is done,
#replace page number name with name of last file with one based on
#Empl_ID.

#rm $Filename # Uncomment to remove the original last file.

exit