Learn how to achieve transparency in Papervisoon3D by reading this tutorial. You can do this easily by changing a default parameter in the MovieMaterial constructor. The parameter called transparent (which is the second parameter in the MovieMaterial constructor) is set to false by default. This is because transparent materials are more computationally expensive than opaque ones. However if you do need to make a material transparent all you need to do is set this parameter to true.
The demo displays the animated MD2 dragon model which is semi-transparent by default, but you can toggle between a transparent and opaque material using the checkbox in the top left hand corner. the source code is attached.