Acrobat 3D

The easiest way to do this is to start by bringing the model into PDF and selecting U3D as the Geometry storage format. Then activate the 3D Annot containing the model, right-click on the 3D Annot and then select 'Edit in the Toolkit'. Create the exploding sequence, or use the key-frame animator to create a custom animation sequence, e.g., for assembly/disassembly or product animation. Then choose 'Save' under the 3D Toolkit. This will push the U3D file back to the PDF file with the new animation sequence embedded.

If you would rather start the workflow in the 3D toolkit, choose 'Save as U3D' from the toolkit after creating the animation sequence and then using the '3D Tool' on the Advanced Edit toolbar to embed the U3D file into an existing PDF, or by creating a new PDF using the U3D model.

I just posted an entry on my blog describing how to do this that includes a flash video demo clip. You can find it [url=http://blogs.adobe.com/mfg/2007/08/roundtrip_edits_between_acroba.php]here[/url].