Annotating a PDF using Preview through Mail app

Hello - I was working on ipad with IOS 13.2.3 and opened a PDF attachment from the mail application and annotated it using an apple pencil. When i finished, I pressed "done" on the top left. When I open the same attachment again, it appears that none of my annotations were saved. Does the Preview app autosave annotated pdf's somewhere? If so, where?

Thanks.