When trying to view an Adobe Sign agreement, or "Download PDF", I am always prompted to download a new version of Adobe Acrobat. I thought using the cloud would automatically have the necessary requirements to view PDFs. After receiving this prompt several times I used the "Get Adobe Reader" option and downloaded the reader, only to have the same issue.
General troubleshooting, How to, Install update and subscribe to Acrobat, Security digital signatures and esignatures
There were changes made to Acrobat/Reader at version XI specifically to support digital signatures for Adobe Sign. Any later version should be OK. If you are seeing this in a web browser, that's because the web browser's PDF viewer doesn't support digital signatures. Download the file and open in Acrobat/Reader.