Finding a direct digital download "game link" for (PES 2018) from official primary stores is currently difficult because the game has been largely delisted in favor of the newer free-to-play eFootball series.

While no longer directly available on the front page of the Steam or PlayStation stores, you can find digital activation keys at several retailers:

However, you can still acquire the game through third-party digital retailers or physical copies. Below are the current options for obtaining the game and its official updates: Digital Purchase Options