If you could find evidence that proves that GameFreak owns the things you say they own, no one would be arguing with you.

There aren't any specific PDFs I can link to because they don't have to exist in order for the property holder to be protected. You will only see tangible documentation in a courtroom and chances of us having access to that is very slim. I already showed examples of laws that would protect them should they ever need to bring that situation to court.

Nintendo, GameFreak or any other software manufacturer can also benefit from several forms of intellectual property protection to prevent copies and imitations, including utility patents but also design patents, trademarks and copyright. Besides intellectual property protection, other protections exist including laws against unfair competition or parasitic copying.

There won't be any specific documents saying, "GameFreak owns the rights to a game that starts with a small child being given his first pokemon by a professor and sets out to adventure... etc etc" it's too specific and unnecessary and precisely why blanket protection exists.