Hmm you could do a bunch of crazy stuff if you assume it will stay digital.

You could have an arbitrarily large page size. You could use color to encode more data… maybe stack QR codes using each channel of a color space (3 for RGB, 4 for CMYK)

There are interesting accessibility and interoperability trade offs. If it’s print-ready with embedded metadata, you can recover the data from a printed page with any smart phone. If it’s a 1 inch by 20 ft digital page of CMKY stacked QR codes, you’ll need some custom code.

Playing “Where’s Waldo” with a huge field of QR codes is probably still way more tractable than handling PDF directly though!