You "think" it's safe, but in reality it's not. If you have thousands invested into something like Bitcoin which is proving to be popular among the minority, which the majority are technical minded then you should really tighten up on security. It may be over the top, but I prefer to be precise and as secure as possible. It's very easy to be infected by a keylogger or other sort of virus.

I would advise not using Word to keep your passwords or private keys in plain text, of course like suggested a LiveCD is actually a good way to think about it and keeping disconnected from the internet and using a Linux based operating system for the LiveCD is probably the best way to go if you have your mind set on storing them on Word/Libreoffice. Printing is always going to be a security flaw, but normally only locally if disconnected to internet & on a clean install of a OS.