I felt compelled to check. Happily, it turns out that if the now-certified-criminal Trump was to become US president once again then he could not pardon himself for the crimes he was found guilty of yesterday.
There seems to be some legal debate on the general topic of “can a president pardon themselves?”. But for these particular cases it’s quite clear that he could not. He was being tried by a state, New York, not the federal government. That means he would need the state to agree to pardon him. Seems unlikely.
From the US Office of the Pardon Attorney:
Does the President have authority to grant clemency for a state conviction?
No. The President’s clemency power is conferred by Article II, Section 2, Clause 1 of the Constitution of the United States, which provides: “The President . . . shall have Power to grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment.” Thus, the President’s authority to grant clemency is limited to federal offenses and offenses prosecuted by the United States Attorney for the District of Columbia in the name of the United States in the D.C. Superior Court. An offense that violates a state law is not an offense against the United States.
Of course that’s not to say he won’t just say he magically pardoned himself anyway. And there’s always the risk of untoward support from the worryingly activist Supreme Court justices. And as some of the many, many pending charges against him are for federal crimes, those ones might be a lot more at risk. But it’s not something he could (legally) do as-is with regards to yesterday’s verdict.
The same applies to any US president of course. For example Biden has no power to pardon Trump of yesterday’s crimes, even if for some bizarre reason he wanted to.