Commonly it is done with a pen or pencil.

Technology!

I've used Optar. It works a lot better than just printing some QR codes. It fits 188 KiB on a sheet of letter sized paper after error correction. It does require a laser printer and a flat bed scanner though.

that is really neat

Storage is easy. Retrieval is more difficult. Test your backups.

Toilet paper do not count

It fits 188 KiB on a sheet of letter sized paper

Maybe I won't use that to back up my photo library as few rough web searches suggests that the pile of paper would be something around 500 meters tall. Pretty neat technology and I suppose if you really need something stored you can etch that to stainless steel plate or something similar, but data density isn't the best around.

This has to be a shitpost.

Transportation of paper-stored data

You can take the sheets with you, send them by post, or even attach them to homing pigeons