In formal and legal writing, "hereafter" is used as an adverb to mean "from this time forward" or "in the rest of this document".
A recent constitutional amendment proposal used the phrase "whether granted heretofore or hereafter " to specify that a rule applies to both past and future actions.
Most commonly, "Hereafter" refers to life after death or the eternal world in religious traditions. "Hereafter" or "hereinafter"? - Google Groups
It acts as a temporal marker indicating that everything following it in a text is subject to the stated condition.