First try to transcode LINK objects with a 'pandoc specific translator.

Fallback to a translator for 'org export if one is not found.

This is specifically to improve interoperability with `org-ref'
(https://github.com/jkitchin/org-ref), which would otherwise reformat
citation links (cite:<reference name>) into a form that breaks pandoc.

ox-pandoc.el

@@ -211,7 +211,8 @@
  :type 'list)
 
 (org-export-define-derived-backend 'pandoc 'org
- :translate-alist '((template . org-pandoc-template)
+ :translate-alist '((link . org-pandoc-link)
+ (template . org-pandoc-template)
  (paragraph . org-pandoc-identity))
  ;; :export-block "PANDOC"
  :menu-entry
@@ -1246,6 +1247,16 @@ t means output to buffer."
  (concat (make-temp-name ".tmp") ".org") s)
  a s v b e (lambda (f) (org-pandoc-run-to-buffer-or-file f format s buf-or-open))))
 
+(defun org-pandoc-link (link contents info)
+ "Transcode LINK object using the registered formatter for the
+'pandoc backend. If none exists, transcode using the registered
+formatter for the 'org export backend. CONTENTS is the
+description of the link, as a string, or nil. INFO is a plist
+containing current export state."
+ (or (org-export-custom-protocol-maybe link contents 'pandoc)
+ (org-export-custom-protocol-maybe link contents 'org)
+ (org-element-link-interpreter link contents)))
+
 (defun org-pandoc-template (contents info)
  "Template processor for CONTENTS and INFO.
 Option table is created in this stage."