There's no need to hide files, just encrypt your file with this software: aescrypt.
Unless you live in a country where refusing to hand over your crypto keys is a crime. Assuming you're hiding your data from the government, not your family, obviously.
your file is perfectly safe for another century or so.
AesCrypt hasn't been cryptographically analysed as much as gpg or pgp, so there could be flaws in the implementation. I'd just play it safe and stick to something else.