-- Stores the key of the auto-generated PDF version of the manuscript.
-- NULL for papers uploaded as PDF (manuscriptKey already points to the PDF).
-- Non-NULL for DOCX/LaTeX uploads where a PDF was generated for reviewer preview.
ALTER TABLE papers
    ADD COLUMN manuscript_pdf_key VARCHAR(500);

COMMENT ON COLUMN papers.manuscript_pdf_key IS
  'Storage key of the auto-generated PDF. NULL when the original upload is already a PDF.';