I've published on my website a free manual in Italian language on privacy and
cryptography with GnuPG on Windows (using gnupg and winpt from GPG4win) and
Linux (using GnuPG command line).
It starts from basic information about digital signing and cryptography, and
explain how to use symmetric and asymmetric cipher, digital sign, web of trust,
key exchange and PKI (keyservers and so on).
If you find that can be handy, it is completely free.