ADE 4.0 requires Mac OS 10.7. All Adobe help and forum answers send me to Adobe Digital Editions downloads. Pressing the link to ADE 2.0 or 3.0 sends me to a blank page. Is it possible to use ADE on my MacBook using its stable current OS 10.6.8 or not? If so, where are the download links available? Posted later: Discovered that Safari downloaded the .dmg without showing anything to that effect. Found the .dmg in downloads folder and installed; appears to function properly.