this code

var tip = "<p class="adobe-reader-download">Most computers will open PDF documents automatically, but you may need to download <a title='Link to Adobe website-opens in a new window'";
tip +=" href='http://www.adobe.com/products/acrobat/readstep2.html' target='_blank'>Adobe Reader</a>.</p>";


if($("div#maincontent a[href*='.pdf']").length>0){
    $("div#maincontent").children(":last-child").after(tip);

works fine with this

<script
 src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"
 type="text/javascript"></script>

but not working with this

<script 
type="text/jscript" 
src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js">
</script>