diff --git a/doc/org.texi b/doc/org.texi
index 39c94aa..f8a5ea2 100644
--- a/doc/org.texi
+++ b/doc/org.texi
@@ -7061,6 +7061,7 @@ is normal.
 @node Exporting, Publishing, Embedded LaTeX, Top
 @chapter Exporting
 @cindex exporting
+@cindex Transient mark mode
 
 Org mode documents can be exported into a variety of other formats.  For
 printing and sharing of notes, ASCII export produces a readable and
@@ -7073,6 +7074,10 @@ deadlines or appointments into a desktop calendar program like iCal,
 Org mode can also produce extracts in the iCalendar format.  Currently
 Org mode only supports export, not import of these different formats.
 
+Org supports export of selected regions when @code{transient mark mode} is
+enabled.  This should always be enabled in default emacs configurations.
+
+
 @menu
 * Markup rules::                Which structures are recognized?
 * Selective export::            Using tags to select and exclude trees
@@ -7605,7 +7610,11 @@ file.
 Export as ASCII file.  For an org file @file{myfile.org}, the ASCII file
 will be @file{myfile.txt}.  The file will be overwritten without
 warning.  If there is an active region, only the region will be
-exported. If the selected region is a single tree@footnote{To select the
+exported.@footnote{Exporting by active region will only work if @code{transient mark
+  mode} is enabled.  This should almost always be enabled.  However, if it is
+not enabled, attempts to export a region will result in exporting the entire
+org file.  If this happens, check the setting of the variable
+@code{transient-mark-mode} in your emacs.} If the selected region is a single tree@footnote{To select the
 current subtree, use @kbd{C-c @@}.}, the tree head will
 become the document title.  If the tree head entry has or inherits an
 @code{EXPORT_FILE_NAME} property, that name will be used for the
@@ -7662,11 +7671,16 @@ language, but with additional support for tables.
 @item C-c C-e h
 Export as HTML file @file{myfile.html}.  For an org file @file{myfile.org},
 the ASCII file will be @file{myfile.html}.  The file will be overwritten
-without warning.  If there is an active region, only the region will be
+without warning.  If there is an active region,@footnote{Exporting by active region will only work if @code{transient mark
+  mode} is enabled.  This should almost always be enabled.  However, if it is
+not enabled, attempts to export a region will result in exporting the entire
+org file.  If this happens, check the setting of the variable
+@code{transient-mark-mode} in your emacs.} only the region will be
 exported. If the selected region is a single tree@footnote{To select the
 current subtree, use @kbd{C-c @@}.}, the tree head will become the document
 title.  If the tree head entry has or inherits an @code{EXPORT_FILE_NAME}
 property, that name will be used for the export.
+
 @kindex C-c C-e b
 @item C-c C-e b
 Export as HTML file and immediately open it with a browser.
@@ -7911,8 +7925,12 @@ references, the PDF output file will be fully linked.
 Export as La@TeX{} file @file{myfile.tex}.  For an org file
 @file{myfile.org}, the ASCII file will be @file{myfile.tex}.  The file will
 be overwritten without warning.  If there is an active region, only the
-region will be exported. If the selected region is a single tree@footnote{To
-select the current subtree, use @kbd{C-c @@}.}, the tree head will become the
+region will be exported.@footnote{Exporting by active region will only work if @code{transient mark
+  mode} is enabled.  This should almost always be enabled.  However, if it is
+not enabled, attempts to export a region will result in exporting the entire
+org file.  If this happens, check the setting of the variable
+@code{transient-mark-mode} in your emacs.} If the selected region is a single tree,@footnote{To
+select the current subtree, use @kbd{C-c @@}.} the tree head will become the
 document title.  If the tree head entry has or inherits an
 @code{EXPORT_FILE_NAME} property, that name will be used for the export.
 @kindex C-c C-e L