Using Automator to take a screen shot from Adobe Digital Editions, Page Down and repeat
Yes, this is possible.

You can use with Script Editor.app or Automator.app for your task. If you choose Automator.app, using the Run AppleScript action to embed your AppleScript snippets.

AppleScript: Simulating key presses

Take a look at using AppleScript to automate key presses, How do I automate a key press in AppleScript? An example from the top answer:

delay 0.5 -- time to release modifier keys if for example the script is run with command-R
tell application "System Events" to tell process "Adobe Digital Editions"
    try
        key down option
        delay 0.1
        click menu bar item 1 of menu bar 1
    end try
    key up option
end tell


AppleScript: Capturing screen shots

To take a screen shot, there are numerous approaches. This question is a good starting point, Take a screen shot and save to desktop with current time as the name:

set theDesktop to POSIX path of (path to desktop as string)
set theCurrentDate to current date
set shellCommand to "/usr/sbin/screencapture " &amp; quoted form of (theDesktop &amp; "Screen Shot" &amp; theCurrentDate &amp; ".png")
do shell script shellCommand


AppleScript: Mouse clicks

Simulating the mouse is trickier but likely possible, see Is there a way to simulate a mouse click anywhere on a screen in Dictate ?. AppleScript's GUI scripting is designed to interact with specific elements on the screen.

Aside: Copyright concerns

Please do not use this process to bypass copyright protection.