Preview.app often lose changes when add text to PDF.
It happens to me a few times that if I add some texts to a PDF, even though I save the changes, they are gone after I close the PDF and reopen again. Besides, some marks after adding the text are also gone. I've even tried to export the edited PDF to another copy. But when I open the copy, there are no changes at all. I have to try a couple of times to make the changes finally applied. I don't think there is anything I did wrong since that's a quite simple operation.
I can't hold back my complaints about how many bugs the Preview.app has and this one is unbearable.
MacBook Pro 13″, macOS 12.0