Paperkey is a command line tool to export OpenPGP secret keys in a format suitable for printing on paper.
Paper can be destroyed easily but it also has amazingly long retention qualities, far longer than the magnetic or optical media that are generally used to back up computer data. So paperkey can be useful in combination with other backup strategies.
Your OpenPGP key as exported by paperkey is still protected by your passphrase.
To learn how to use paperkey, read the documentation on the paperkey website.
For example, to export an OpenPGP secret key using paperkey, execute the following command, replacing [keyid] with the ID of the key that you want to export:
gpg --export-secret-key [keyid] | paperkey | gedit