Documentation for version 4.x

I apologize if I’ve overlooked something obvious, but I cannot seem to find any documentation for ACF which is specific to the free version 4.x

I need to include ACF with a free theme and version 5 which is premium only states that to include ACF with a free product I must use version 4.x, yet I cannot find the documentation specific to that version.

Any thoughts or helpful URLs would be appreciated

https://www.ads-software.com/plugins/advanced-custom-fields/