karls-mac-mini:monks karl$ perl -MImage::ExifTool=:Public -E 'say ImageInfo("./pdf/a.pdf")->{CreateDate};'
2015:01:07 14:46:51
karls-mac-mini:monks karl$ ls -hl ./pdf/a.pdf 
-rw-r--r--  1 karl  karl    48K  7 Feb 14:46 ./pdf/a.pdf