Lets encrypt is hands down the easiest way to secure your web server communications with SSL. On Ubuntu the process is simple and the configuration automagically takes care of all the http to https redirects. I’ve used Letsencrypt to secure many WordPress installations running on various Apache based VPS.
1.) add the Certbot repository to the Ubuntu package system:
sudo add-apt-repository ppa:certbot/certbot
2.) Install the package:
sudo apt install python-certbot-apache
3.) Configure an SSL cert and associate it with your domain:
sudo certbot --apache -d yourdomain.com
When asked if you want Certbot to handle the redirects press 2:
Certbot verifies your domain through the existence of an Apache virtual host. If you do not have a virtual host configuration file you will need to set one up.