Hi Marc,

re:
> Some programs preserve layers as groups in the PDF, it might be a workaround but I have
> no idea how much work would be involved.

There is a thing in PDF called "optional content groups", and MoI's PDF export does set those up currently. They will show up in Adobe Reader's layer palette where you can hide and show them.

But Adobe Illustrator does not seem to read them in as layers when opening a PDF file, I'm not sure about other software.

If I remember right, the PDF "optional content groups" don't quite match up exactly to regular layers because of stuff like an object can belong to more than one of them I think.

If you have an illustration program that can round trip layers to a PDF file, can you please e-mail me (moi@moi3d.com) a simple example file (like with just a couple of lines on a couple of different layers) so I can take a look at how it's structured?

- Michael