requires: poppler_utils, bc
find . -name '*.pdf' -exec pdfinfo {} \; | grep Pages: | grep -Eo '[0-9]+' |  paste -s -d + - | bc      
requires: poppler_utils, bc
find . -name '*.pdf' -exec pdfinfo {} \; | grep Pages: | grep -Eo '[0-9]+' |  paste -s -d + - | bc