Question

Is it correct that saving a PDF to the harddisk first, and then opening it from there with some PDF reader (not the browser) is safer than opening it directly with the browser plugin?

My current understanding

I know that the PDF browser plugin might have a security leak and a manipulated PDF file might exploit it and get access to the user's computer.

I recently heard that saving the PDF file frist and opening it then was safer. I don't understand why that should be safer. Can anyone explain?

My logic would suggest that a manipulated file started from the harddisk can just as well exploit a security leak, say for instance, of Adobe Acrobat Reader.