diff --git a/cpdf.ml b/cpdf.ml
index b883ea6..cc5e978 100644
--- a/cpdf.ml
+++ b/cpdf.ml
@@ -2389,10 +2389,13 @@ let select_pages range pdf =
 
 (* Upright functionality *)
 
-(* If all pages are already upright, do nothing to save time. *)
+(* If all pages are already upright, and the mediabox is (0,0)-based, do nothing
+to save time. *)
 let allupright range pdf =
   let page_is_upright page =
-    page.Pdfpage.rotate = Pdfpage.Rotate0
+    page.Pdfpage.rotate = Pdfpage.Rotate0 &&
+      (let (minx, miny, _, _) = Pdf.parse_rectangle page.Pdfpage.mediabox in
+         minx < 0.001 && miny < 0.001 && minx > ~-.0.001 && miny > ~-.0.001)
   in
     not (mem false (map page_is_upright (select_pages range pdf)))
 
diff --git a/cpdfmanual.pdf b/cpdfmanual.pdf
index 0ac3669..62919e9 100644
Binary files a/cpdfmanual.pdf and b/cpdfmanual.pdf differ
diff --git a/cpdfmanual.tex b/cpdfmanual.tex
index 6798304..f3fd82f 100644
--- a/cpdfmanual.tex
+++ b/cpdfmanual.tex
@@ -792,7 +792,7 @@ ninety degrees clockwise. Does not change the page dimensions.
   \label{upright}
    \noindent The \texttt{-upright} operation does whatever combination of
 \texttt{-rotate} and \texttt{-rotate-contents} is required to change the
-rotation of the document to zero without altering its appearance.
+rotation of the document to zero without altering its appearance. In addition, it makes sure the media box has its origin at (0,0), changing other boxes to compensate.
 
   \section{Flipping Pages}
 \index{flip pages}