One of my clients asked me about SSL for his website which is hosted on Windows Server 2012 IIS. I advised him to go with either Lets Encrypt or Cloudflare Reverse Proxy.
My reasons are simple both options are free to use and offer same level of encryption even better than some paid solutions (Looking at you SHA1 SSL providers) , Cloudflare is easier to setup though as you don't have to install any software on your server just use Cloudflare's provided nameservers and you are ready to go.
First download and install this handy tool CertifyTheWeb.
Once done you will be introduced with this screen :
B. Choose your IIS domain from this select menu.
C. (Optional) If B is not showing any domain. you can type your domain manually and you will need to verify it manually (locating www root, etc...).
Once you Select your domain from B or add domain in C you will be introduced with Figure 2.
B. I don't use it. some kind of test before actual request I will assume .
C. Click this once you are ready to get your free SSL Certificate .
Once you click on C you will be introduced with another screen showing the progress of your request and whether it succeeded or failed.
What I like about CertifyTheWeb is the auto renewal feature it has. I rarely login to my clients servers to find their SSL expired and not renewed .