diff --git a/docs/howto/outputting-pdf.txt b/docs/howto/outputting-pdf.txt
index 9950c4316c..986a5b252c 100644
--- a/docs/howto/outputting-pdf.txt
+++ b/docs/howto/outputting-pdf.txt
@@ -67,6 +67,7 @@ Here's a "Hello World" example::
 
         # FileResponse sets the Content-Disposition header so that browsers
         # present the option to save the file.
+        buffer.seek(0)
         return FileResponse(buffer, as_attachment=True, filename='hello.pdf')
 
 The code and comments should be self-explanatory, but a few things deserve a
diff --git a/docs/ref/request-response.txt b/docs/ref/request-response.txt
index 22cc016057..30ad0ccf42 100644
--- a/docs/ref/request-response.txt
+++ b/docs/ref/request-response.txt
@@ -1106,6 +1106,8 @@ Attributes
 
     If ``open_file`` doesn't have a name or if the name of ``open_file`` isn't
     appropriate, provide a custom file name using the ``filename``  parameter.
+    Note that if you pass a file-like object like ``io.BytesIO``, it's your
+    task to ``seek()`` it before passing it to ``FileResponse``.
 
     The ``Content-Length``, ``Content-Type``, and ``Content-Disposition``
     headers are automatically set when they can be guessed from contents of