Is it permissible to use Photoshop downloaded from the internet, knowing that the producing company does not pursue those who distribute its software, unlike other companies?

It is not permissible to copy programs whose owners state that their rights are reserved, except with their permission. This is because these are proprietary rights for which they have expended effort and money, and copying them without permission invalidates these rights and wastes their efforts. However, if there is no text prohibiting downloading and use, then there is no objection, and the prevailing custom is to be applied in determining whether permission exists or not.