What does "(SECURED)" mean in the title of Adobe Reader?

I opened a PDF that I haven't looked at in a while and noticed that in Adobe Reader, the title becomes "filename.txt (SECURED) - Adobe Reader"

Can someone tell me what the "(SECURED)" denotes?

(Prior to today, FoxIT Reader had been my default PDF program, but due to work-related issues, I had to switch back to Adobe.)

Solution 1:

It means that the file is encrypted.

To quote Steven Madwin, an Adobe Employee:

the application puts it in the title bar as a visual clue that the user is in an encrypted file. The default is for the application (either Acrobat or Reader) to display the file name, encryption status, and the application name in the title bar. You can replace the file name with the document title, but you cannot suppress the encryption status. This was added to Acrobat 8 because too many users were viewing encrypted PDF files and didn't understand why they couldn't make changes.

Solution 2:

It means the file is protected in some way, there are restrictions on what you can do with it.

"If you receive a PDF that is protected by security features, you may need a password to open the document. Some protected documents have restrictions that prevent you from printing, editing, or copying content in the document. If a document has restricted features, any tools and menu items related to those features are dimmed."

http://help.adobe.com/en_US/Reader/8.0/help.html?content=WS58a04a822e3e50102bd615109794195ff-7d75.html