Just to add a bit of info, the nice thing is, if you share your files via OneDrive, users can click the link you send them and open the file in PowerPoint Online, which is basically PowerPoint running your file in a browser. And that's free. So they shouldn't even need to have PowerPoint proper.
They can also download PowerPoint apps on their phones and tablets, etc. The apps are also free. That said, the apps use the model where you may need to pay for a subscription to Office to access certain features. Those are only needed if you're creating files, though, not viewing. (And all the basic features are free. The pay-for features are not basic features, so you may not even need to pay for a subscription in order to create basic presentations, either.)
I think that's the solution. Thanks.