diff --git a/src/documentation/skinconf.xml b/src/documentation/skinconf.xml
index 22061a1..c6c4f63 100644
--- a/src/documentation/skinconf.xml
+++ b/src/documentation/skinconf.xml
@@ -9,9 +9,14 @@ be used to configure the chosen Forrest skin.
 
   <!ENTITY % links.att 'name CDATA #REQUIRED'>
   <!ENTITY % link.att 'name CDATA #REQUIRED href CDATA #REQUIRED'>
-  <!ELEMENT skinconfig (disable-search?, searchsite-domain?, searchsite-name?, project-name, project-url, project-logo, group-name?, group-url?, group-logo?, host-url?, host-logo?, year?, vendor?, trail?, credits?)*>
+  <!ELEMENT skinconfig (disable-search?, searchsite-domain?, searchsite-name?,
+  project-name, project-url, project-logo, group-name?, group-url?, group-logo?,
+  host-url?, host-logo?, year?, vendor?, trail?, credits?)*>
   <!ELEMENT credits (credit*)>
-  <!ELEMENT credit (name, url, image, width?, height?)>
+  <!ELEMENT credit (name, url, image?, width?, height?)>
+  <!-- id uniquely identifies the tool, and role indicates its function -->
+  <!ATTLIST credit id   CDATA #IMPLIED
+                   role CDATA #IMPLIED>
   <!ELEMENT disable-search (#PCDATA)>
   <!ELEMENT searchsite-domain (#PCDATA)>
   <!ELEMENT searchsite-name (#PCDATA)>  
@@ -86,5 +91,8 @@ be used to configure the chosen Forrest skin.
       <width>88</width>
       <height>31</height>
     </credit>
+    <!-- A credit with @role='pdf' will have its name and url displayed in the
+    PDF page's footer. -->
   </credits>
+
 </skinconfig>