Normally, all previous versions are located in the shadow, so if you right click a published document from within the web folders, go to properties and then the third tab, versions you can view older versions.
If you want to do this in code:
<pre>
strURL = "url of the last published version"
Set oVersion = New PKMCDO.KnowledgeVersion
Set prmRs = oVersion.VersionHistory(strURL)
Set oVersion = Nothing
</pre>
prmRS will contain a recordset, which contains the url to the old versions in the shadow.