apex:include

CommonIncludedPage.page

<apex:page id="commonIncluded">
    <apex:includeScript value="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js" />
</apex:page>

IncludedDemoPage.page

<apex:page id="page">
    <apex:include pageName="CommonIncludedPage"/>
    <apex:form >
        <h1>Included Demo</h1>
    </apex:form>
    <script>
        $j = jQuery.noConflict();
        $j(function(){
            $j('h1').css( "color", "red" );
        });
    </script>
</apex:page>