During setup, you can choose between Server Core (headless, recommended) or Server with a GUI (full desktop experience).
Choose your preferred language and select the 64-bit ISO option. Download W2012R2 Server ISO
Save the ISO file, which is typically around 3-4 GB. Crucial Technical Requirements & Notes During setup, you can choose between Server Core
If you are a Volume Licensing customer, you can download the full retail/volume ISO under the Billing > Your products > Volume licensing tab. Steps to Download (Evaluation Center) Download W2012R2 Server ISO
You will need to sign in with a Microsoft account and fill out registration details.
Go to the official Windows Server 2012 R2 download page.
This is the primary, free, and legal source. You can download a 64-bit ISO for a 180-day evaluation.