In some occasional cases, books purchased from the Kobo store must be read or run through Adobe's Digital Editions software. What is the benefit to this requirement, why use Digital Editions specifically, and what happens in the process?
According to the Kobo website:
When do I need to use Adobe Digital Editions?
If you use any of Kobo's free reading apps or a Kobo eReader, you may never need to use Digital Editions at all. Kobo's reading apps and eReader can automatically download most books from the Kobo Store, and update your library with them.
The exceptions are when:
You want to read eBooks from another store or from a library on a Kobo eReader;
You buy Adobe DRM PDFs from the Kobo Store and want to read them on a Kobo eReader;
You want to read books from the Kobo Store on an eReader from another company.
In these cases you will need to use Digital Editions to open your books and transfer them to your eReader.
The reason for this is that most eBooks from online booksellers and libraries are protected by Digital Rights Management (DRM). DRM prevents the unauthorized copying or redistribution of eBooks, to protect the rights of authors and publishers. There are different types of DRM, but Kobo supports a version by Adobe. This is why you may need to use Adobe's software, Digital Editions, to open and transfer some eBooks to your eReader.
Also, when you buy a book from the Kobo store, you often receive an
ACSM file (I have received this type of file often when buying ebooks from the Kobo store for my Sony Reader PRS-650). An
ACSM file is a license file that Adobe Digital Editions will first verify and then download the appropriate ebook.
UPDATE (I should have read further down... they mention the ACSM files on the same page as linked above):
Why did I get an ACSM file when I downloaded my book from the Kobo Store?
Your Kobo eReader can read books in EPUB and PDF format. (A file format is how books are stored on your computer.) If you downloaded a book and received an ACSM file, don't worry – this isn't a problem. The ACSM file is the license for the PDF or EPUB book you bought. To get the book itself you just need to open the ACSM file in Adobe Digital Editions. Digital Editions will verify your license and then download your eBook in either EPUB or PDF format. You can then transfer your book to your Kobo eReader (or another compatible eReader).
You will get a license file if you download a book that is protected by Adobe Digital Rights Management (DRM). DRM prevents the unauthorized copying or distribution of books, to protect the rights of authors and publishers. Most books in the Kobo Store are protected by DRM.