add links to similar projects

README.md

@@ -61,6 +61,15 @@ echo "you might need to restart your shell"
 ```
 
 
+--- 
+
+## Similar Tools 
+- python GUI for rearranging pdfs for printing: https://github.com/theodubus/pdf2book
+- JavaScript web GUI for rearranging pdfs for printing: https://momijizukamori.github.io/bookbinder-js/
+- Java GUI for pdf bookbinding: http://quantumelephant.co.uk/bookbinder/bookbinder.html
+- Java GUI for PDF manipulation: https://github.com/itext/itext-java
+
+
 --- 
 
 ## pdf2book.py