If the objects are identical, and also searchable, then there are only one method I can possible think of:
- Install Libre Office and open the PDF file in the Draw application.
- Make a script (python or visual basic) that search for text snippets that are identical.
However, there are several possible problems that can make this undoable, at least as I know of:
- There must be possible to traverse document objects in Libre Office Draw.
- The objects themselfs have to be equally formatted. My experience with PDF files (at least vector graphic on pages imported via Inkscape) is that even when the content looks very similar, it's a huge pile of mess when trying to tell different parts/objects from each other)...