diff --git a/book/preamble.tex b/book/preamble.tex
index 7ae2ae0..b388186 100644
--- a/book/preamble.tex
+++ b/book/preamble.tex
@@ -45,6 +45,12 @@
 \usepackage{makeidx,showidx}	% showidx breaks hyperref when loaded before hyperref
 
 
+% put line numbers on every page
+\usepackage{lineno}
+\linenumbers
+
+
+
 
 %\usepackage{url}