diff --git a/README b/README
index 30aba8a3f..18c296fdd 100644
--- a/README
+++ b/README
@@ -633,10 +633,16 @@ Citation rendering
     `--metadata citation-abbreviations=FILE`.)
 
 `--natbib`
-:   Use natbib for citations in LaTeX output.
+:   Use natbib for citations in LaTeX output.  This option is not for use
+    with PDF output, since pandoc will not automatically run bibtex in
+    producing the PDF.  It is intended for use in producing a LaTeX file
+    that can be processed with pdflatex and bibtex.
 
 `--biblatex`
-:   Use biblatex for citations in LaTeX output.
+:   Use biblatex for citations in LaTeX output.  This option is not for use
+    with PDF output, since pandoc will not automatically run bibtex in
+    producing the PDF.  It is intended for use in producing a LaTeX file
+    that can be processed with pdflatex and bibtex or biber.
 
 Math rendering in HTML
 ----------------------