Docu Sign

I received and e-mail through my Mac e-mail account. with an attachment, that I need to sign.

I clicked on the attachment and the document comes up in Acrobat Reader DC.  It  says that in the top near a tool bar that “Certified by Adobe Sign, a Document Cloud solution,<adobe-sign-certified@adobe.com>, Adobe Systems Inc, certified by VeriSign CA for Adobe”  When I go to click on the document itself--it will not allow me to sign anything--it is just merely a hand icon that I can hover over the signature line--but it will not allow me to sign it.  What do I do?

[Moved from the Adobe LiveCycle General discussions - features, feedback, training, documentation, etc. forum and into a more appropriate forum. - moderator]