diff --git a/Makefile b/Makefile.in
similarity index 58%
rename from Makefile
rename to Makefile.in
index 21ab83486fd8da53d7e024aea1d6832eadf23950..59d72ae75143a45ff762b1377b258dfc0c3f56e2 100644
--- a/Makefile
+++ b/Makefile.in
@@ -1,6 +1,11 @@
+PDFLATEX = @PDFLATEX@
+
 preprocessor.pdf: preprocessor.tex expr.png expr-sharing.png matrices.png overview.png
-	pdflatex preprocessor
-	pdflatex preprocessor
+ifdef PDFLATEX
+	$(PDFLATEX) preprocessor
+	$(PDFLATEX) preprocessor
+endif
 
 clean:
 	rm -f *.pdf *.toc *.aux *.log *.nav *.snm *.vrb *.out *~
+.PHONY: clean