diff --git a/functions/pdf.xml b/functions/pdf.xml
index a8c1241d97..b5aeaa3519 100644
--- a/functions/pdf.xml
+++ b/functions/pdf.xml
@@ -27,6 +27,12 @@
     of <function>pdf_set_font</function> has changed to a string. This
     means that instead of e.g. 4 you have to use 'winansi'.
    </simpara>
+   <simpara>
+    If you use pdflib 2.30 the <function>pdf_set_text_matrix</function>
+    will have gone. It is not supported any more. In general it is a good
+    advise to consult the release notes of the used version of pdflib
+    for possible changes.
+   </simpara>
    <simpara>
     Please consult the excellent documentation for
     pdflib shipped with the source distribution of pdflib.