The answer is simple:
it's a literary, elegant, way to exactly describe the extremely difficult situation a bladerunner finds themselves in:
at all moments they are "on a knife's edge," if you will, between: total disaster, horrible consequences, appalling moral decisions, immediate overwhelming physical danger, in a horribly troubling historical-social milieu, where every outcome is very bad for society and the bladerunners themselves, and the impossibly difficult decisions they have to make, are at the very heart of these problems...
If you think of phrases like: "between a rock and a hard place" or "on a knife's edge" or "no rest for the wicked" or "nowhere to run to baby, nowhere to hide" or "walking on broken glass" ....... being a "blade runner" is a really wonderful, literate, turn of phrase added to the language:
as soon as you hear it - the idea of running along a razor blade! - you're immediately in a place where you're rushing as if in battle, with horrors both behind and ahead, and there's a horrific bloody mess if you fall in any of four directions or you pause for a second ... gruesome!
So, it doesn't "mean" something specifically (there's no key or plot connection): Just as other great names or invented terms from literature don't "mean" anything ... Holly Golightly, Horatio Honrblower, Professor Dumbledore ... but these connected words are incredibly suggestive, both precisely, emotionally and subconsciously:
so, it's just the outright greatest "invented future slang term", and it epitomizes the horrible, urgent, nightmarish dilemma (... both existential and immediately physical ...) which Deckard and Batty find themselves in.
(I think it's incredible the way HF played Deckard as just a man - no superspy heroics, no great philosophical certainty .. he's just a man ... for example, when Leon's about to kill him
he's no hero in a tank-top, just a guy running on the "edge of a knife" through life, with no real solutions, no answers, just questions and immediate danger.)