Hi candide,

> Besides 3D PDF, which I didn't know existed until now
> and I still don't understand the reason for its existence
> - what does it have going for it?

It can be helpful for communication. For example say you're working on a model for a client and you want to show them some intermediate results, and you'd like for them to be able to rotate around and view things from different angles but they do not actually have much direct experience in 3D modeling themselves.

In that kind of situation you can probably send them a 3D PDF file, which they can probably view on their system without needing to go through extra steps to install other software because they have the Acrobat reader installed already.

- Michael