diff --git a/build.sh b/build.sh
index 64e0afb..c23170c 100755
--- a/build.sh
+++ b/build.sh
@@ -1 +1,3 @@
-groff -R -Kutf8 -mom -Tpdf 00-front.mom 01-preface.mom 02-microsound.mom 03-convolution.mom 04-phase_vocoding.mom 05-alternative_tunings.mom > cooganl-sound-hacking.pdf
+rm *.pdf
+OUT="cooganl-sound-hacking-v.$(git rev-list --count master)"
+groff -R -Kutf8 -mom -Tpdf 00-front.mom 01-preface.mom 02-microsound.mom 03-convolution.mom 04-phase_vocoding.mom 05-alternative_tunings.mom > $OUT