Adobe ACROBAT 3D Manual page 743

Upgrading Digital Editions
If you owned and read Digital Editions using an earlier version of Acrobat, you need to
migrate these files to Acrobat 7.0. The first time you open My Digital Editions bookshelf
or try to read a Digital Edition using Acrobat 7.0, you are prompted to migrate files to
Acrobat 7.0. Follow the on-screen prompts.