Notes to external files

It is often necessary to make a small text note to the PDF file or image. These are usually tags or links to other notes. It would be useful to be able to do this without creating additional notes.
I don’t know how to implement this yet, so I invite you to discuss it.
For clarity, I will give an example.
I have an article in the PDF. I place it in my knowledge base. since the PDF can’t be linked to other notes, I have to create a new note where I put the author’s name, the area to which the article belongs, and so on. All this is necessary for the article to be linked to other notes.
I would like to have the opportunity to avoid the establishment of subsidiary notes.

If you place the PDF, or a link to it, in a note, why would you need to add details that are present in the PDF?

I would like to avoid creating an additional note, but still be able to link the file to other notes, for example, through back links

You could add the PDF link directly to the other notes. I don’t see how you could have backlinks without having links in the first place

Sounds as if you’re asking for Obsidian to treat PDFs as if they were notes?

I’ve no idea what would happen if you just added .md to the name. Obsidian couldn’t open it of course, but I don’t know whether it would reject its existence.

Other apps may provide a solution to this. With DEVONthink (macOS/iOS), for example, you can provide links to PDFs with page numbers so that you jump right to the correct page. I’m sure that’s available in other PDF editors, too.

Yes!
Or give a way to make a small note in the PDF or image, without creating an additional md file

You can edit metadata stored directly in pdf file, accessible through some pdf viewers.

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