Best plugin to make printable origami with on SketchUpMake?

The download from from Pumpkin Pirates site is a .zip file, download and change the file extension to.rbz. You can then use the Preferences install extension button to install it.
I’m not familiar with the specifics of how it works on a mac but there is a video linked to this thread that does show you how on a mac. It’s about half way through the video.