I've understood that there is no "native" way to automatically import stuff from a given folder in the Mac version of Evernote, without resorting to AppleScripts that may or may not work after an update to either the operating system or Evernote.
But, in the Windows version you can do this from Evernote itself.
So this is something of a workaround, but if you use Dropbox or any other Cloud storage service (who doesn't these days?) AND you have access to a Windows computer that stays on most of the time, like a media sharing machine at home, your computer at work, in the basement or whatever,