Okay, I figured it out. Thanks to Pippen for pointing me to the newer repository.
Steps taken:
apt update && apt -y install ca-certificates wget net-tools gnupg
wget -qO - https://as-repository.openvpn.net/as-repo-public.gpg | apt-key add -
# Change the <DISTRUBTION> to your release. For me, it was trusty, which is Ubuntu 14.04
echo "deb [arch=amd64] http://as-repository.openvpn.net/as/debian <DISTRIBUTION> main">/etc/apt/sources.list.d/openvpn-as-repo.list
apt update && apt -y install openvpn-as
Verify upgrade:
cd /usr/local/openvpn_as/etc/
cat VERSION
You should get this output:
export AS_VERSION=2.7.5
export AS_BUILD=932a08a3