An alternative with Powerpoint is to save it as a PDF file. Most operating system will recognise a PDF and you can go from page to page and back quite easily. You may lose a little screen width, but that's not terrible.

Tip: As others have said - DO NOT LEARN ON THE DAY! I'm giving a presentation on Monday next to launch our annual village Garden & Arts Festival, with a PP presentation. All compiled, examined, edited, tested days ago. The presentation is at 7.30pm - I'll be testing the equipment that afternoon...