If you're creating a slide-show presentation in Keynote, you may need to change the size of the slides to fit a certain aspect ratio. Slides in a Keynote presentation are not limited to a particular size, but the program has few sizes to choose from. Upon launching the program, Keynote defaults to a slide size of 1024 x 768 pixels, but it can be changed to larger sizes, depending upon your projection or print requirements.
Click the Keynote icon on your dock. The "Theme Chooser" window will open. Select "Open" from the "File" menu, then navigate to an existing Keynote presentation on your Mac. Alternatively, select an icon in the "Theme Chooser" window to start a new presentation with your chosen theme.
Select the blue "Inspector" icon in the Keynote menu to choose another slide size or customize your own size. Select the "Document" icon, which appears as the first icon on the left pane of the "Inspector" window."
Click the pull-down menu next to "Slide Size" to choose larger sizes than are available in the "Theme Chooser" window. Click "Custom slide size" to set your own height and weight size in pixels. Click "OK."
- If your Keynote slide show contains HD movies, select a higher resolution theme with a resolution of 1920 x 1080 pixels. This slide size requires more memory. Not all themes in the software offer this slide size.