What he's seeing is just the file preview. Have him click the blue Download button in the top right corner of the page. It will download the original PPT file. If he uses the browser's save functionality all he will be saving is the PDF preview.
We love to learn from the educators who use Dropbox. Whether you teach kids, teens, adults or a combination of all three, we want to know what apps and integrations you use with Dropbox to help with teaching. Which of the ones below is your favorite, or most used tool?