How can we add watermark in visualforce pdf?

Hi,

<img src=”{!URLFOR($Resource.tran_watermark)}” width=”100%” height=”100%” style=”position:fixed; background-repeat:repeat; left:0cm; top:0cm; z-index:0; display:{!IF(quote.status == ‘approved’, ‘none’, ”)}”/>

go through the following link which gives a sample code you can test in your org to create a watermark on PDF generated by a VF :
http://www.opfocus.com/blog/how-to-watermark-a-visualforce-pdf/