<!-- Page: -->
<apex:page id="thePage">
    <apex:outputText value="(page) This is the page."/><br/>
    <apex:include pageName="Namespace.ManagedPageName"/>
</apex:page>

<!-- Page: include -->
<apex:page id="theIncludedPage">
    <apex:outputText value="(include) This is text from another page."/>
</apex:page>