PDF not showing up

Hello, I have installed this plugin and set up three PDF to be viewed using it. However, when I click on the view page link the page is blank. The PDF viewer comes up but not the PDF. See what I mean by viewing my website here: http://benjaminperry.org.uk/?page_id=219 or the PDF viewer here: http://benjaminperry.org.uk/?publications=labour-manifesto-2015

https://wordpress.org/plugins/wppdf/