She tried to download into Adobe Reader but got an error message that it could not be downloaded. Any suggestions?
The link that you would have downloaded is a ZIP file (so "Open In Adobe Reader" wouldn't have been your answer), so you would have needed to save it to your drive and then extract it. Within the ZIP file, there will be a PDF containing the book, a PDF containing the sample puzzles Berry discussed in the book, and PUZ files of the puzzles. Even if you could opened it within Adobe Reader, you would have lost the file to consult in the future. Bottom line: Save to disk and then back it up.
If the link still works, save it to file instead of doing what you did. If it doesn't, try contacting Patrick Berry via his posted e-mail on his website (he's generally responsive the times I've e-mailed him), explain what happened, and see what he might do to make sure you receive the data, and a refund of the second purchase (if you didn't want to buy it twice).