MN4 can recognize and identify duplicate imported documents automatically, and memorize deleted documents in a notebook?

I imported a pdf document (let’s call it a.pdf) to a notebook and a local folder of MN4. Then I deleted a.pdf and imported another pdf document (let’s call it b.pdf).
a.pdf and b.pdf are actually two different electronic scans (they have different sizes and different names) of the same book.
However, when I imported the b.pdf to the same notebook and the same local folder, the b.pdf didn’t appear in the notebook and the local folder. Instead, the deleted file a.pdf was restored again!
So is there a hidden function in MN4 which can automatically recognize and identify the pdf documents, so if the newly imported document is recognized as a duplicate of an old document, the MN4 automatically refuses the new document and opens the old document?
And is there another hidden function in MN4 which can somehow memorize the deleted document, so if a duplicate new document is imported, MN4 refuses the new document and restore the deleted old document instead?
If my conjectures are right, then I don’t think these functions are necessary, because now I only want to get rid of the old document a.pdf and import the new document b.pdf.

Hello

It is recommended that you take a look at the MN4 official manual: https://www.wolai.com/89rjeaKjQmD9m2kygMQeJE the content you do not understand is basically here to get answers, you can use shortcut ctrl + p to search for the problem you want to know to learn

Kind Regards,

Support Team

I don’t think anything in the document you sent me can solve my problem.