Powerpoint via Google
You can create a non-downloadable slide presentation on Google Drive following these steps:
1. Upload the powerpoint to drive just like a video -
2. Once uploaded, double click on the file to open in the Google Drive "player"
3. In the top menu middle, click on the "Open with" toggle, and select "Google Slides"
4. It will show an progress icon indicating it is converting
5. When icon is done, exit out by clicking on the <---- arrow in the upper left, and you'll see there is now a second Google Slides version of the presentation.
Select this file to set share and no download permissions.
6. Open the Advanced feature in the share box and set as follows: