I've set up an offline wallet (Armory - Ubuntu OS - offline computer) and now want to print the private keys as a backup in case my offline computer (older laptop) crashes/dies.
What type of printer can I use to be sure that the printer does not store the private key data? Which type of printers should be avoided? Any advice/suggestions would be appreciated.
I recommend getting a paper and pen and writing it down manually. Some printers have a cache that will save the backup, also if you are using a networked printer an attacker sniffing your network will be able to get your backup.
Armory paper backups aren't that hard to write out.
EDIT: You need to use the backup feature of Armory to do this. Don't write out the private keys themselves, Armory wallets are deterministic, you only need to make one paper backup and you're good to go forever, no need to make additional backups when you add new addresses.