There are many tools available for the Linux user to encrypt a file ( https://askubuntu.com/questions/160253/encrypting-decrypting-a-single-file-in-ubuntu-12-04-lts , etc).

I want to [1] encrypt a single PDF on my Linux OS, [2] email it to a non-technical user on a Mac and [3] expect they can easily decrypt the PDF (using a password I provide through “another channel”).

Ideally, the non-technical recipient is not required to install additional software. Preferred (fool-proof) solutions involve native-to-MacOS (built-in) capabilities or, perhaps, double-clicking a password-protected “self-extracting” file … minimal experience or thinking needed.

My knowledge of MacOS is thin. Suggestions?

( Side question – first post from a no-longer-virgin Stack Exchange user.
Should this have instead gone to https://unix.stackexchange.com/ ?)