Yes you can add multiple public IP addresses to a single server.
You will need to subscribe for the static IP addresses you need to add to the server as this can’t be achieved using DHCP.
The primary IP address will be the one you select from the network settings tab of the server detail modal window in the web console.
If you then want to add further static public IP addresses you do this by manually editing the IP configuration on the server itself.
You should specify the primary static IP address and any additional static IP addresses in your account that you would like to add to the server in the server’s IP configuration files.
Just make sure that you only use static IP addresses that are in your account and that are not in use by other servers that you have.
It is worth keeping a note of the additional static IP addresses you are using with that server so that you don’t assign any to another server in your account.
In this way you can add as many public IP addresses to a server as you want, you just need to do make sure you subscribe for the static IP addresses that you need, manually configure these on the server and track their usage.