I don't think so. PGP scrambles the text of the message for you (that's the body), but you're still using the standard email protocol, which sends attachments without making changes to them. You'd need to encrypt the files before sending them. (And the recipient would have to unencrypt them manually.)
I think it very easily could. Email bodies are often MIME Multipart messages [0], which can be nested to arbitrary depth. You can see an example of such a message here [1]. The PGP setup used by default with Mutt will encrypt your cleartext multipart message (which contains your text, html, and attachments) and then send only the new cyphered body.
