Open the app and tap on Downloaded to see the Editions that are currently stored on your device. Tap the cover of an Edition.
1) If the Edition has been updated since it was downloaded, you will see two options, Update or Archive. Selecting Archive will remove the Edition from your device, but retain your ability to download it again in the future.
2) If the Edition has not been updated since it was downloaded, tapping the cover will take you into the Edition.
3) From here, swipe down to bring up the menu, then tap the Thumbnails icon (four vertical lines).
4) This will present all the pages of the Edition as thumbnails, and a button at the bottom of the page Archive. Selecting Archive will remove the Edition from your device, but retain your ability to download it again in the future.