Flippress is a German startup that is currently in the process of creating a website that will allow everyone to create their own customized paper keyboards which can be used as any normal keyboard on the market with the difference that it is completely made of paper.
To get into more detail: The paper keyboard consists of three layers of paper. Conducting paths are printed on the top and bottom paper while the middle paper separates the other two. The middle paper has holes that connect the two other papers when a key is pressed which basically has the effect that the signal is send to the computer.

The paper keyboards use the Open Source software Autohotkey to define and change the keyboard shortcuts. This means you do not purchase a normal keyboard which you can use to type but a specialized keyboard.

Autohotkey is however not the only possibility to use the paper keyboard. Using an USB Adapter would be another solution, softwares that have the support build in and self created scripts that interpretate the keys presses two other possibilities.
This means that the paper keyboards should be plattform independent.
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Haha, I could make my keyboard from wood, and then stick paper one on it :D
Hmm, very interesting.. “Is it a huge bookmark in that book? – Nah, that’s just my keyboard..” :D