People re-use slides for different audiences. And 10 years ago, you would still be able to skip a few slides quickly when they contain confidential information if - by accident - you forgot to delete the product roadmap that you used in last week's Board meeting. (Or you forgot to mark them as "hidden").

The smart phone with super high resolution cameras means that nothing is safe anymore. There is the accidental smartphone snap, but also the professional "slide harvesters" diligently recording every slide in your deck. An HD video just needs a millisecond to capture the slide that is being skipped.

Here are some other confidentiality pitfalls to watch out for:

• Data that still sits in the underlying Excel sheets, even when you take the data labels of your chart
• Hidden slides in presentation mode that are there for everyone to see when you send a PowerPoint file
• Speaker notes
• Collaborator comments
• File names or URL names that can still persist in a document even after its is PDF-ed
• Tiny footnotes that give away important information

Cover image by Ben White on Unsplash