Possible challenges: OCR (optical character recognition) if the PDF isn't text-searchable. Integrating interactive elements without compromising the original content. User engagement and keeping the feature updated if the PDF is revised.

I should consider the target audience—probably high school or university students studying geometry. Teachers might also need tools to assess students. The feature should be user-friendly, accessible on mobile or web, and aligned with the content of the PDF.

Let me outline possible steps. First, analyze the content of the PDF to identify key topics—lines, angles, shapes, theorems, etc. Then, determine how to digitize these. If the PDF has exercises, an interactive exercise system would be useful. Perhaps integrating a virtual whiteboard for solving problems. Video tutorials or animations could explain complex concepts like Pythagorean theorem or similar triangles.