Acrobat Pro 9.4.5 digital signing, menu gray but properties says allowed

Question

I have a document that had the signing menu gray/disabled. I tried going to Advanced->Security->Remove Security.
The dialogue said "You Cannot change security on this document because the document enables extended features in Adobe Reader. You can save a copy without the xtended Reader features using File->Save A Copy."
I saved a copy, but in the new document the "Remove Security menu prompts for a password.
The new doc's Security properties are::
but the menu for signing is gray/disabled. Is there a way I can sign this document?

Answer 1

Thank you George. I've been using the digital signing facility for about a
year now, and never have seen a digital signature field. Usually I'm signing
PDF's that are not  forms, but plain PDFs. I use the typewriter tool to type
over the PDF where there are lines or blank spots, then use the Place
Signature facility to draw the signature region/box and have Acrobat pop in
the JPG of my signature.
Which Document Restriction needs to be changed to "Allow" in order for this
document to be signed the way described above for other PDFs?