“For example, if Gerald Ford had issued his pardon of Richard Nixon in secret, what would have prevented Jimmy Carter from conveniently losing the notes on that particular order and letting the DoJ proceed with the case anyway? Nixon would need to publicize his pardon, or at the very least broaden the number of people who were privy to its existence, if he wanted to use it as a defense, and he’d need to do extra work just to prove that the pardon was legitimate in the first place.”
Exactly. Hillary and Obama would not need to announce that Obama had pardoned Hillary unless and until the Trump administration tried to prosecute her.
At that time, Hillary would announce that she had received the pardon.
I would guess Hillary would insist that any such secret pardon include Huma and Cheryl and her other flying monkeys.