Howtoforge posted a tutorial about setting up ProFTPd + TLS on Ubuntu 11.04

FTP is a very insecure protocol because all passwords and all data are transferred in clear text. By using TLS, the whole communication can be encrypted, thus making FTP much more secure. This article explains how to set up ProFTPd with TLS on an Ubuntu 11.04 server.

  Setting Up ProFTPd + TLS On Ubuntu 11.04 (Natty Narwhal)