diff --git a/cpdfmanual.tex b/cpdfmanual.tex
index c9b0357..c429b63 100644
--- a/cpdfmanual.tex
+++ b/cpdfmanual.tex
@@ -1,6 +1,7 @@
 %Document -split-max
 %Document -spray
 %Document -info-json, -page-info-json, -page-labels-json, -list-fonts-json
+%Document subformat information
 \documentclass{book}
 % Edit here to produce cpdfmanual.pdf, cpdflibmanual.pdf, pycpdfmanual.pdf,
 % dotnetcpdflibmanual.pdf, jcpdflibmanual.pdf jscpdflibmanual.pdf etc.