The VIC-20 user's manual included specs for all the port pin-outs, and the reference guide came with the full schematics of the computer itself.
I suppose that one could argue that with the complexity of modern computers, this would not be feasible, but it shows how things have changed.
The Commodore 8-bit line (and to some extent the Amiga) were made to be tinkered with and hacked. The VIC-20 was in a way the Arduino of its day.
