Misc PDF files NOT backed up in Norton Security with backup

I have many PDF files throughout my documents folders.  There is one directory where 12 of 53 pdf files are not backed up and I get no error from Norton.  These were all downloaded from my insurance company  I get around it by "including" all of the files in that folder.  This works but what about new docs downloaded?  I will say that all of the affected pdfs were consecutive in a date range...Feb - Mar 2013...everything before and after gets backed up no problems.  The files properties all match whether backed up or not.  This was happening with Norton 360 as well.