Why modification protected PDF documents cannot be indexed by IFilter 11 with SharePoint Search?

Question

Hello everyone!
I have a SharePoint farm which stores a big number of protected PDF documents. Those PDF documents are protected against modification and printing! They allow copy of content and screen readers though.
I had IFilter 9.0 installed and I saw that none of my protected documents could be found... I decided to upgrade the IFilter to its latest version (11) in order to be sure it was not something which was already fixed.
Problem is that even with IFilter 11, my protected PDF documents are still not indexed! Is that a limitation of the IFilter? What kind of security configuration does the IFilter component supports?
Thanks in advance for your help!!
Carlos

Answer 1

I will try to be the most complete possible on the security settings of my document:
I do NOT ask a password in order to open the file
I do ask a password in order to modify the document:
Printing allowed: NONE
Modification allowed: NONE
Activate the copy of the text, pictures and other content: Checked
Activate the access to the text by screen readers: Checked
Options
Compatibility is set on Acrobat 7 and later
Encrypt the entire document option is checked
When I apply those settings, save the document and then open the security settings tab with Acrobat Pro I see that everything is forbidden except the three following options:
Copy of the content
Copy of the content for accessibility
Extraction of the pages
When I close the document and open it again with Acrobat Pro or Reader I see that only two options are enabled this time:
Copy of content
Copy of content for accessibility
So basically it seems the PDF document looses the Extraction of the pages privilege once I close Adobe Acrobat Pro.
PS: I am translating the security options from French so they may not be the exact ones you see on your Acrobat Pro if you have it in English.