E-Sign Greyed Out

I have an end-user who can e-sign any document that is created by us, there are no issues. As soon as she and her co-worker recieve a PDF to sign from external companies the option is greyed out. They have had multiple documents come from external parties that would not allow them to e-sign on.

I checked the security settings for the PDF's and they were marked as being ALLOWED to sign. I've tried updating the application. I've tried to remove the application and install/update again. I've also tried to use tools such as Revo Uninstaller which help delete files/folders/registery keys left behind after an uninstall and removed those items, as well. This still would not work for the e-sign capabilities.

Again, other documents are fine to sign. I suggested to the end-user that it could be the way the sender is setting up the documents, but there haven't been any signs of the document properties showing this to be the case.