Assuming that you really do mean a linked PDF atttachment (with the chain link icon), then Zotero does not delete the actual file when you delete a linked attachment - it only deletes the link. https://www.zotero.org/support/attaching_files#linked_files
That's probably more often a problem for people who *want* the PDF deleted; for which the delitem plugin can be used (to delete both the item and its linked PDF, or just the linked PDF). https://github.com/redleafnew/delitemwithatt
Thank you for your explanation. I was misled by the name of this option. I use Zotero in the Russian language. In Russian translation, it is "Move the document to the trash". But the correct must be "Delete link".
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https://www.zotero.org/support/attaching_files#linked_files
That's probably more often a problem for people who *want* the PDF deleted; for which the delitem plugin can be used (to delete both the item and its linked PDF, or just the linked PDF).
https://github.com/redleafnew/delitemwithatt
If you are a Zotero 6 user, install "delitemwithatt" from here: https://github.com/redleafnew/delitemwithatt/releases/tag/0.1.06
For Zotero 6 you can get the latest version from here: https://github.com/redleafnew/delitemwithatt/releases/latest