@gordonpym wrote:
…Could Endnote somehow add this pdf as an attachement automatically?
Unfortunately no. You will need to manually attach the PDFs.
An alternative method with limited application might be to use Endnote’s auto import function to import the PDFs which in turn will 1) create an Endnote record, and 2) automatically attach the PDF (providing the PDF has metadata to enable creating the Endnote record). PDFs that don’t have the metadata would generate incomplete Endnote records.