Comment by cyphar

Actually, after my comment I took another look and it turns out that only a few months ago someone released a pure-Rust PDF renderer called hayro[1] that seems to fit exactly what I need, so I will work on finishing this bit of paperback as soon as I have some spare time. Pure image scanning (with a webcam, phone camera, or uploading a photo) will also work since QR code scanning libraries like rqrr support scanning all QR codes in an image.

[1]: https://docs.rs/hayro/latest/hayro/