To delete a previous edition, please follow these instructions:
1) Open the app and tap 'Downloaded' at the top
2) Tap on the edition you would like to delete
3) Pull the screen down with your finger and tap the icon in the top right corner which looks like four vertical lines
4) This will show all the pages in the edition and offer an option to "Archive" at the bottom of the page
5) This will delete the edition from your device, but retain your right to download it again at a later date.
If you go to that edition afterwards, you will see that it will ask you to download it as it is no longer saved to your device.