Use the Slide Master view in Microsoft PowerPoint to customize the look and feel of your slides and create a consistent view for your presentation. You may wish to create multiple master slides ...

They are displayed horizontally, with slide numbers starting from one, but there are features in PowerPoint that allow the user to change the slide’s size and orientation.

You can change the size of a slide in your PowerPoint presentation through the "Design" menu on the Windows PC, Apple MacOS, and web-based apps.

Launch PowerPoint 2007. Click the Windows button to open the handout presentation with the page numbers to change. Click the "View" tab. Click the "Slide Master" button on the ribbon.