For people who have had problems uploading ePubs in ADE and are getting the tiny fonts...I wrote to Kobo and they've given me steps on how to fix the problem.
1. Plug the device into your computer
2. Launch ADE and click on the Kobo icon on the left hand side.
3. Delete all the ePubs you've put onto the device
4. Go to the kobobooks.com website and log into your account
5. Make sure all the books you want on the reader are in your library
6. Open up the Kobo Desktop app and click "update library".
7. Click "Sync"
That will update your files and fix the tiny font problem. It can take a while though...mine took about an hour before it was finished.
Unfortunately they didn't provide me with a fix if you've bought your books from a source other than them.
I hope this helps some people.