It requires good amount of time to locate the PayPal REST SDKs download Github Location
We will make it easier for you.
Java
Download from here https://github.com/paypal/PayPal-Java-SDK
.NET
Download from here https://paypal.github.io/PayPal-NET-SDK/
Node
Download from here https://paypal.github.io/PayPal-node-SDK/
PHP
Download from here https://paypal.github.io/PayPal-PHP-SDK/
Python
Download from here https://github.com/paypal/PayPal-Python-SDK
Ruby
Download from here https://github.com/paypal/PayPal-Ruby-SDK
