We have released an update today that fixes the digital signing issue. This update will be automatically applied to all existing installations of Acrobat and Reader DC. You can also open Acrobat or Reader DC and visit Help > Check for updates to make sure you are on the latest patch.
Details about the release: Release notes | Adobe Acrobat DC, Acrobat Reader DC | Update, November 03, 2016
Please let us know how it goes.