Marking up PDFs

I am trying to annotate a PDF that is public domain but as soon as I touch the document in mark up mode, I get a dialog box that says “without the owner password, you do not have permission to save this document.” I’ve uploaded it to kindle, ibooks, and adobe reader and I get the same response from all apps (adobe says liquid mode isn’t available in protected mode). Other people have downloaded the exact same PDF and can make annotations. What gives?!!