It may take until the turn of the year 2014/2015, depending on the settings in your Office 365 tenant. Then, each document library can be protected in SharePoint Online with IRM. And, as we can see later, can also be synchronized to my offline library OneDrive for Business on my computer. Microsoft has announced this on his office blog on 19/11/2014

 

But to take this affect, you have to do some setting as an Office 365 administrator:

Switch as an administrator to the Office 365 admin Center – service settings – rights management and the click on Manage

The click on “activate”. now you have enabled IRM for your Office 365 tenant.

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Now you have to search in the SharePoint Admin Center beneath “settings” the section   information rights management

 

Activate “Use the IRM service specified in your configuration” : Click also on “Refresh IRM settings, you should not see any error message. Go down on the side and press the “OK” Button.

Now you have to change to the library, you want to protect with Information rights management (IRM).

Click on “Library” and then on “Library Settings”

Click on “Information Rights Management”

You have to activate and now the library is protected with IRM. Give an description, the user may see later in each document

you may also click “Show Options”. Here you may do more setting, f.e. To disable print or Restrict a period for accessing a downloaded document or  …

Don’t forget the click on “OK”. Now the library is protected with IRM, all documents still in the library are protected and new documents also.

If you have enabled IRM for the library, you are no longer see the preview of the document.

	If you open a document with Word online, you see the IRM message, which you describe above.
	The same message apply, if you open a document with Word 2013.

If you want to sync a document library protected with IRM to you local device, using OneDrive for Business, you must consider, that you have installed 2 Updates on your Windows Device.

There are two windows patches: KB 2899513 , I have written a blog post here. It#s also a good idea to install patch KB 2899510 , I have described it here

Without these updates, OneDrive for Business is not able to sync these documents to your local device and you got several error messages.

what will happen with IRM?

only these people, who have access to the document library may open and work with these documents. If you share a document to other people,who has no access, these people will not able to open or work with the document.

Here is an example: I want to open a word document protected with IRM with Wordpad.    Normally, you may do that, but you are not able to open the document, because the protection is in the document itself. Therefore you got an error message.