: Use the Unity Personal license. It is free for individuals and small businesses making less than $100k/year.
: Unity provides structured PDFs for educators and students, such as this Unity 2018 Installation & Basics Plan . Unity 2018 for Mac Free Download
: Unity 2018 generally requires Mac OS X 10.9 or higher. If you are on a very old system like El Capitan (10.11) , stick to version 2018.4.26f1 for the best results. : Use the Unity Personal license
If you are looking for documentation or guides ("helpful paper") to get started with this specific version: including 2D and 3D project templates.
: You can find archived Unity Learn tutorials that match older workflows, including 2D and 3D project templates.