The search for is evolving. We are now seeing the rise of "enhanced PDFs" that include QR codes leading to 360-degree video rotations. Some modern PDFs for tablets include layers that allow you to toggle skin, muscles, and bones on the same page.

If you are looking to purchase physical or authorized digital copies, you can access them directly from the creators:

Example 2 — Forearm Supination/Pronation Study:

It breaks complex body parts into basic 3D shapes, making it easier to construct a figure from scratch.