There is a slight misconception here, DA is not a Google metric. It is a MOZ metric (and a very useful one) Google no longer publishes their authority score.
As things are currently secure webpages are not a make or break. Google says that if you are collecting people's information, payment information or other sensitive data you should use a secure page. However, if you are just telling somebody how to reinstall Windows 10 it's probably not a big deal.
It will probably become more of an issue as time goes on, but currently there are still a number of online shops which are not secure and they rank reasonably well.
That said, where ever possible always use SSL (or to give it its official name TLS).