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Forgive me for my ignorance but, I recently purchased an eBook only to find that I also had to download Adobe Digital Editions in order to be able to view it on my Mac. The PDF that I downloaded in the process is encrypted. Does this mean that I can only view it using Adobe Digital Editions, or can any ePub Reader (including any that I install under Windows) be able to read it?

I know that there are many (better) ePub readers out there, the prominent ones of which are listed in the following post.

What could I use to read epub books on OS X?

If I now were to install Calibre, for example, would it interfere with Adobe Digital Editions?

Note that I bought the eBook from http://www.ebook.com. This is the message I get when I try to double click on the PDF file to open it using Acrobat Reader:

This document requires digital rights management (DRM) features supported
by Adobe Digital Editions. Would you like to open it in Digital Editions now?

This is the information that I have been able to retrieve about the file using Adobe Digital Editions:

Permissions set by the publisher
  Allow viewing: on any device
  Allow copying: 5 copies with an additional copy accrued every 6 days,
  capped at 5 copies, on any device
  Allow printing: 20 pages with an additional page accrued every 1 day
  12 hours, capped at 20 pages, on any device
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It'd help to know where you downloaded the eBook from? What format was the eBook in? –  Aaron Lake May 1 '12 at 3:38
    
I downloaded the eBook from www.ebooks.com. The format is PDF encrypted with Digital Rights Management (whatever that is). I will update the question to include this and other information that I have been able to retrieve about the file. –  Bill May 1 '12 at 9:11
    
Note that pdf and epub are different formats and questions on one do not normally help to deal with the other. It so happens ADE reads both. Reading PDFs is down with Preview etc but not deal with the DRM –  Mark Jul 10 '13 at 15:21
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2 Answers

ePub is a digital publishing format, but it's not as straightforward as you might hope, in that not all ePub files are the same. There are 3 main types of ePub in the wild today:

  • Straight ePub, any ePub reader should be able to open these
  • ePub with Digital Rights Management protection:
    • Adobe Digital Editions
    • Apple iBooks from the iBooks store

The protection mechanisms are portable to an extent, you can see the Digital Editions protection on other formats other than ePub. The main takeaway is that to read the file, you need a compatible reader. For the non-protected files, that is straightforward enough. Pretty much anything can read them. For the protected ones, it's more difficuly. Adobe protection is compatible with a small number of desktop apps for a bit of extra portability, but iBooks ones can only be opened in iBooks in iOS, full stop.

It's a pain, and like the MP3 fuss we are starting to see people dropping DRM entirely from their ebooks.

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I have to admit, it is the first time I have seen DRM placed on a PDF, which unfortunately does require Digital Editions to view it. Another eBook that I purchased last year allowed me to download it in three different formats: Plain PDF, ePub and MOBI. –  Bill May 1 '12 at 13:56
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The single most important thing to remember is the point mentioned by stuffe about the iBookstore. Do not buy books there if you want to read them on your Mac or PC. They can only be read on an iOS device, and some (those in .ibooks format) can only be read on an iPad. No app exists (not ADE or Calibre or any browser add-on) which will let you read a DRM'd iBook on a Mac or PC.

Not all iBooks have DRM (e.g. those published by O'Reilly do not), but it is impossible to tell which ones fall in that category.

Most other sources for ebooks I have seen have a FAQ or Help page which explains what software is required to read its books on what devices.

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Unfortunately, this eBook requires Digital Editions in order to be able to view it. –  Bill May 1 '12 at 13:58
    
@Bill Why do you consider the need for ADE to be such a problem? –  Tom Gewecke May 1 '12 at 16:43
    
I don't consider ADE a problem. The problem is only being able to use ADE to view the file. Insofar as using other viewers, note that I have purchased Adobe Creative Suite 5 (not for this reason) and, while InDesign allows one to export a document in ePub format, there is no way to import a document in ePub format! Being an Adobe product, I would have expected some sort of compatibility without having to download a separate (albeit Adobe) product. –  Bill May 1 '12 at 23:41
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