Emacs-org-mode and latexmk

The org-mode mailing list was useful! I added (setq org-latex-to-pdf-process (list "latexmk -f -pdf %f")) to my .emacs file and then C-c C-e d worked as expected, producing the PDF using latexmk.

Note if org-mode-version > 8.0 org-latex-to-pdf-process has been renamed to org-latex-pdf-process

In Org mode 8, the variable is renamed. As Shitikanth commented, I needed %f, so in org 8: