A very small (but rather important, depending on occasion/readership) detail:
[...]
gpg --encrypt --sign --armor -r recipient@email -r your@email.com filename
[...]
-r recipient Specifies recipients of the message. You must already have private keys of the people listed. [...]
The author probably meant, "You must already have public keys of the people listed," not private. (Probably just a typo-level thing, they doubtlessly know what they are talking about.)
Glad somebody else pointed this out. I read that and thought it should have said "public" too, but the rest of the article was so strong that I started doubting myself and felt like I was going crazy.
A very small (but rather important, depending on occasion/readership) detail:
The author probably meant, "You must already have public keys of the people listed," not private. (Probably just a typo-level thing, they doubtlessly know what they are talking about.)