Practical Applications of Public-key Cryptography: Securing Email Communications with PGP. An 11 page tutorial that discusses practical uses of PGP desktop, the commercial version of PGP.
You can download it from the following link: https://packetstormsecurity.com/files/download/38606/practical-public-key-crypto.pdf
Source: https://packetstormsecurity.com/files/38606/practical-public-key-crypto.pdf.html