To do Alt + J + P + M on Mac in PowerPoint, download and install Accelerator Keys, then press Option, followed by J, P, M.
Command: Compress Pictures
This is how to do Alt + J + P + M on Mac in PowerPoint with Accelerator Keys, the native ribbon and alt key shortcut solution for Mac users who get more done with PowerPoint.
Alt + J + P + M opens the Compress Pictures dialog in PowerPoint. This allows you to reduce file size by compressing images, which is useful for reducing presentation file sizes while maintaining acceptable image quality.