for file in $(find -type f -iname '*_??????????.pdf' -mtime -1)
do
    echo $file
done

for file in $(find -type f -iname '*_??????????.pdf' -mtime -1)
do
    echo ${file##*_}
done

for file in $(find -type f -iname '*_??????????.pdf' -mtime -1)
do
    echo ${file%.*}
done

echo ${${file##*_}:0:10}
echo ${(${file##*_}):0:10}
echo ${${file##*_}%.*}
echo ${{file%.*}##_}
echo ${${file%.*}##_}