I think you may have to put “file+sys:/“ before your path.

For example: file+sys://Users/nate/some_pptx.pptx

Best,
Takaaki

> On Sep 27, 2019, at 18:42, Nathan Neff <nathan.neff@gmail.com> wrote:
> 
> Hello all,
> 
> I have a simple path in org-mode
> 
> /Users/nate/some_pptx.pptx
> 
> When I press C-c C-o it opens the file in binary mode in Emacs.
> 
> A path to a PDF will actually open the file with the associated program:
> /Users/nate/some_png.png -> Opens in Preview when I press C-c C-o
> 
> How can I get emacs / org to open pptx files in the same fashion as if I had
> double-clicked using Finder on Mac?
> 
> Thanks,
> --Nate