There is another part of the site that deals with paper comics, but think that's more of a database, I don't think they sell them.
Here's the main page
for the paper comics, if you want to get back to the digital there from there just click comics by comixology. I just checked and you can't buy the paper comics from comicxology, but they do link to Things From Another World.
For anyone who wants to see how their digital comics work, here's this week's free digital sneak peek from DC
. (The comics featured are the one that just came out in physical format this week, not digital).