I have a PDF file that is partially restricted: I am able to leave comments, but not make general changes. It works as expected on the desktop version of Acrobat (on a Mac). But when I open the same file on my iPad (from a shared Dropbox folder), I am unable to leave comments. Instead, when I tap the little pencil and then “Comment,” I get the message: “Read-only PDF: This tool is not available because the document is read-only.”
Thus there is a bug in the iPadOS version of Acrobat, and I hope Adobe can fix it as soon as possible.