CDRs are most reliable way to backup important documents for several years.
My cool dry Colorado basement (high temp is about 67) has been good and many disc from the 1990s are perfectly readable
Now I'm getting curios on how long my data can retain on a SSD without powering on it...
https://www.anandtech.com/show/9248/the-truth-about-ssd-data...
Putting a label on a CD-R kills them extra fast.
QR codes are one of the first sort of barcodes to come to my mind for storage; but I'm reminded of how poorly they encode text compared to analog characters on a printed page. The printed letters are also a technology that is already known and self documenting. If you can understand the content there's no intermediate representation.