Subject says everything that needs to be said.

U3D is a finicky pile of junk. The big three (3d Studio Max, Maya, and Cinema 4d) do not support this idiotic format and will not directly export a U3D file.

Converting from one of the many useful file formats to U3D is an exercise in frustration that your Acrobat Pro users shouldn't be exposed to.

Please put this file format back into the hole it crawled out of and provide support for a real 3d format.

I would personally suggest either FBX or even better, GLTF / GLB. Every single major 3d program exports in these formats and it allows the model to be exported with its textures.

I am sick and tired of spending hours trying to get a perfect, beautiful model exported into U3D only to end up with a low-res model that may or may not have its textures while simultaneously being forced to try to explain to the client who wanted the model embedded in a PDF why it doesn't look like it did on the screen.

U3D hasn't been updated in SEVENTEEN YEARS.

Please. Please abandon this junk.

Thank you.