pdf will not open in mail

I am having issues with opening pdf attachments in email. When I click to open, a blank page pops up that says about:blank. It will download the pdf to my download folder. I have to click on that and then open the pdf.
This is very time consuming when I have a lot of pdfs to open. I amusing adobe acrobat, which is up to date as well as Mozilla which is up to date.
Any suggestions?