Can the new owner see my old performance reviews and use them against me?

Generally, yes, in the same way they can generally access the rest of your personnel file — performance reviews are typically treated as part of the employment records that transfer along with an ongoing business, so the new owner can understand who they're employing and administer things like continuity of service properly.

That access isn't the same thing as the new owner being entitled to use old reviews unfairly or as an excuse to treat you worse than your actual, current performance warrants. A review from years ago, especially one tied to circumstances or a manager who's no longer around, shouldn't be treated as the last word on how you're doing now — a fair employer looks at your actual, current conduct and performance under the new ownership, not just what an old file says.

If a new manager brings up an old review in a way that feels unfair or is being used to justify a decision that doesn't match your recent work, push back and ask that your current performance be assessed on its own terms. Keeping your own copies of anything important from your file, positive reviews especially, is a sensible precaution during any ownership change.