validate PDF files using pdfcpu (https://github.com/pdfcpu/pdfcpu)

check.bash

#!/bin/bash

find . -name "*.pdf" -print0 | while read -d $'\0' file
do
        /usr/bin/pdfcpu validate -q "$file" &> /dev/null

        if [ $? == "1" ]; then
                ((if++))
                echo "$if) $file PDF file is invalid."
        else
                echo "."
        fi
done