Index: /trunk/doc/manual/en_US/user_VBoxManage.xml
===================================================================
--- /trunk/doc/manual/en_US/user_VBoxManage.xml	(revision 35159)
+++ /trunk/doc/manual/en_US/user_VBoxManage.xml	(revision 35160)
@@ -2849,4 +2849,41 @@
             </glosslist></para>
         </listitem>
+
+        <listitem>
+          <para><computeroutput>updateadditions</computeroutput>, which allows
+          for updating an already installed Guest Additions version on the
+          guest (only already installed Guest Additions 4.0 and later).</para>
+
+          <screen>VBoxManage guestcontrol updateadditions &lt;vmname&gt;|&lt;uuid&gt;
+            [--source "&lt;guest additions .ISO file to use&gt;"] [--verbose]</screen>
+
+          <para>where the parameters mean: <glosslist>
+              <glossentry>
+                <glossterm>uuid|vmname</glossterm>
+
+                <glossdef>
+                  <para>The VM UUID or VM name. Mandatory.</para>
+                </glossdef>
+              </glossentry>
+
+              <glossentry>
+                <glossterm>--source "&lt;guest additions .ISO file to
+                use&gt;"</glossterm>
+
+                <glossdef>
+                  <para>Full path to an alternative VirtualBox Guest Additions
+                  .ISO file to use for the Guest Additions update.</para>
+                </glossdef>
+              </glossentry>
+
+              <glossentry>
+                <glossterm>--verbose</glossterm>
+
+                <glossdef>
+                  <para>Tells VBoxManage to be more verbose.</para>
+                </glossdef>
+              </glossentry>
+            </glosslist></para>
+        </listitem>
       </itemizedlist></para>
   </sect1>