Use ghostscript to convert PDFs to version 1.5 (better for pdflatex)

ghostscript_pdf_1p7_to_1p5.sh

#!/bin/bash 
set -e
outfile=$2
if [ "$#" -eq 1 ]; then
    outfile=$1
fi
gs -sDEVICE=pdfwrite -dNOPAUSE -dBATCH -dSAFER -dCompatibilityLevel=1.5 -sOutputFile=temp.pdf $1
# so you can run on the same file
mv temp.pdf $outfile

pdf_1p7_to_1p5.sh

#!/bin/bash 
set -e
for var in "$@"
do
    ./ghostscript_pdf_1p7_to_1p5.sh $var
done