You may wish to make your PowerPoint read-only to discourage edits or prevent accidental edits.
1. Open the presentation you want to make read-only and select the File tab.
2. You’ll then be in the Info menu. Select Protect Presentation to open a drop-down menu. Click Mark as Final.
3. A dialogue box will then appear, letting you know the presentation will be marked as final and saved. Click OK.
Information sourced from: https://www.howtogeek.com/437502/how-to-unlock-read-only-powerpoint-presentations/