This section of code displays the products_description ... if you added on to it a more information button it would be at the end of the description ...

If you want to add a button or text to where the add to cart button is, then you need to locate that part of the code in that file ...

If you look through the case statements you will see where the various parts of the listing are built and can add the button or text to any portion of it ...

Try to add:
Code:
. '<br>Hello World'
to any part of the code to test where it is being added ...