Wierd connection between the original pdf file and the imported file in MN

I need help with a problem I am experiencing.

I am experiencing two problems that makes me suggest that there is a wierd link between the file in my i-pad downloads folder that I imported in MN and the file in the documents and study mode that I annoated after importing.

First, when I delete the file in the downloads folder, file in the document mode and the study mode in MN goes blank.

This is wierd since I understand that the file that I imported to MN and the orignal file in the documents should be seperate. I don’t want there to be a link between that original file and the file I am working on after I imported to the app. But this suggests me that there is a link.

Which leads to these questions:

  1. Is this a bug?
  2. If not how can I protect myself from losing the the annotated file in the MN app? Does this mean that I should protect and keep the original file in some place safe even though it does not show any annotations that I have added in the MN app?

Second, when I import the same file from the downloads folder which I have already imported in the past to the documents in MN in order to make a different file with different annotations based on the same file, this simply cannot happen.

Only, the name of the previously imported file changes to the orignal file name in the downloads folder.

Does anyone have answers to my problem?