In case you have a paper in your library where the main PDF file is actually a supplemental PDF file and you want to add a new primary PDF file to the paper, you can do it with the following steps.

  • Select the paper in your library.
  • Go to Paper > Attach File, or use the keyboard shortcut shift + cmd + O.
  • Select the file that you want to use as the main PDF file and click 'Attach'.
  • Papers shows a 'Paper already has an attached PDF' dialog.
  • Select 'Replace current PDF with new PDF' and check 'Keep current PDF as a supplemental data'.

Attach a file and replace the current PDF as a supplement in Papers for Mac

Read more about adding supplemental files on Papers for Mac.