How to Spell-Check Your PowerPoint 2013 Presentation After-the-Fact
Repeat the last two steps until PowerPoint gives up.
When you see the following message, you’re finished: Spell check complete. You’re good to go!
PowerPoint always checks spelling in the entire presentation, beginning with the first slide — unless you specify a single word or group of words by highlighting them first. PowerPoint checks the spelling of titles, body text, notes, and text objects added to slides. It doesn’t check the spelling in embedded objects, however, such as charts or graphs.