The extension is not available. You can use the Internet Explorer.
To be more blunt about it, Microsoft currently does not support such extensions/plug-ins and thus Adobe cannot supply one.
Thanks for the info. I suspected something of the sort, but was surprised when I couldn't readily find a simple answer. When I looked for extensions/plugins for Edge, I found very few available. I figured some sort of API availability issue.
Norton has a Password Vault and Search extension for Edge; Microsoft has an extension for OneNote 2016. I don't see any reason why Adobe could not now make an Acrobat DC extension for Edge. It would sure be appreciated.
Of course Microsoft can make extensions! You might find this interesting. Windows 10: Why does Microsoft Edge have only 70 extensions after a whole year? | ZDNet
Interestingly in 2015, Microsoft were saying "it would not support any add-ons except Flash Player" ActiveX support in Microsoft Edge Browser - Microsoft Community