For example, I just added a CD insert for a live moe. show to the playlist for the music. I added "moe." as the artist, and added the name of the album so it shows up with the rest of the music. iTunes won't try to play it, nor will it copy the PDF file to your iPod when you sync. But if you ever want to read those liner notes or view the insert, just double-click the file entry in your iTunes library.
I discuss the possible ramifications of this feature in this article on my site...

