You do not need to keep track of each version. I think that with 1.8 there are no significant changes that can affect the article, so if it is from 2009, it should work.
Along with http://framework.zend.com/downloads/archives you can also check out http://framework.zend.com/changelog
:
1.0 - 2007
1.5 Zend_Form, Zend_Layout - 2008 .
1.8 Zend_Application - 2009 ., bootsraping
1.9 Php 5.3 - 2009 .
1.10 ControllerTestCase - 2010 .
1.11 Zend_Cloud - 2010