Hi,
I've posted this question to other forum and I was suggested to post it here.
PROBLEM:
My problem is setting "protect document" -> "restrict access" -> "Restricted Access" to up 12000 word/excel documents. (check image)

By opening a word document and then going to "protect document" -> "restrict access" -> "Restricted Access" and checking "Restrict Permission to this Document" and then adding users in Read / Change -
I'm able to choose the users that can read and change the document with ease.
The goal is: If someone that has access to the document decides to email the document to you, I ensure that you cannot open it. That's what this is all about - It's an important goal.
This restriction goes beyond in setting the folder permissions it's a change inside the document.
QUESTION:
Is there a way to have this done via PowerShell, bash, API c#?
Other posts:
I've posted this in Word forum and I was suggested to ask here.
https://social.technet.microsoft.com/Forums/office/en-US/44b235da-3d71-4a43-bb4a-e57c51d451bd/protect-document-restrict-access-to-12000-winword-documents?forum=word
http://answers.microsoft.com/en-us/office/forum/office_2013_release-word/protect-document-restrict-access-to-12000-winword/a39d345e-3d38-4ef9-a1da-9eb12154b395
Thanks in advance.
João