A presentation can have only one page size and orientation (either landscape or portrait). The Page Setup dialog allows you to change the page size and orientation of all slides in the presentation.

Slide Size

You can select a popular slide size or set a custom slide size.

Slide Width

It presents the width of the slide. You can also change it.

Slide Height

It presents the height of the slide. You can also change it.

Slide Orientation

You can change all the slides in your presentation to orientation you want. Switching orientation will swap the width and height of the slides.