updated website to include the 'stable' version of the book

Author: mpd37

index.md

@@ -9,7 +9,7 @@ Twitter: [@mpd37](https://twitter.com/mpd37), [@AnalogAldo](https://twitter.com/
 
 We wrote a book on Mathematics for Machine Learning that motivates people to learn mathematical concepts. The book is not intended to cover advanced machine learning techniques because there are already plenty of books doing this. Instead, we aim to provide the necessary mathematical skills to read those other books.
 
-The book will be [published by Cambridge University Press](https://www.cambridge.org/au/academic/subjects/computer-science/pattern-recognition-and-machine-learning/mathematics-machine-learning?format=PB&isbn=9781108455145) in early 2020.
+The book will be [published by Cambridge University Press](https://www.cambridge.org/academic/subjects/computer-science/pattern-recognition-and-machine-learning/mathematics-machine-learning?format=PB) in early 2020.
 
 We split the book into two parts:
 
@@ -21,7 +21,11 @@ We aim to keep this book fairly short, so we don't cover everything.
 **We will keep PDFs of this book freely available after publication.**
 
 
-## Download the [PDF of the book](book/mml-book.pdf)
+## Downloads
+### [PDF of the printed book](book/mml-book_printed.pdf)
+This version is equivalent (modulo formatting) with the printed version of the book
+### [PDF of the book](book/mml-book.pdf)
+This version is the most up-to-date version of the book, i.e., we continue fixing typos etc.
 
 
 ##  Table of Contents