I am familiar with a product that did this. At 600 dpi we stored 1.8M of data on an A4 page with ~30% ECC codes. QR codes were not designed for this. To get th

I am familiar with a product that did this. At 600 dpi we stored 1.8M of data on an A4 page with ~30% ECC codes. QR codes were not designed for this. To get this reliable there were many image processing, coding and practical issues to solve.