How to convert 3D PDF
to Collada?

3D PDF is a PDF file with 3D geometry inside. Using any 3D PDF enabled viewer, rotation, zoom and part selection is available within the 3D view.

3D PDF is just like a normal PDF (Portable Document Format) file, which contains a 3D view somewhere on some page. Just like a PDF containing an embedded image, except when you put the mouse over it, you can rotate, zoom, pan and explore the scene in 3D (three dimensions). The file actually contains a 3D geometric representation of the scene, not just images from different viewpoints.

Collada (COLLAborative Design Activity) is an interchange format for interactive 3D applications. Originally developed by Sony Computer Industry, now it is managed by the Khronos Group, a member-funded industry consortium, which now shares the copyright with Sony, Recently Collada has been well adopted by ISO as a publicly available specification, ISO/PAS 17506.

It is an XML-based schema that allows data exchange among 3D Digital Content Creation tools, such as SketchUp, Maya, 3ds Max, and Rhino. COLLADA files have the *.dae file extension, which stands for digital asset exchange.