This was created by scanning an original printed edition. This softcover book is in scanned image format because original digital layout files never existed or were no longer available from the publisher.
This has high-resolution scans of an original copy of the book and is authorized by the publisher. It is essentially digitally re-mastered.
One of the hidden gems of 5th edition adventures in my opinion. PCs get from 1st to 10th+ level by the end.
Enjoy.