Have you tried holding Ctrl/Opt and drag-dropping when adding the pdf link? That will create a valid external link to a file (and clicking it will open the file in its default app).
Some examples below of linking to external files and folders:
Have you tried holding Ctrl/Opt and drag-dropping when adding the pdf link? That will create a valid external link to a file (and clicking it will open the file in its default app).
Some examples below of linking to external files and folders: