How Can I Tell If My Pug Is Full Blooded?

You have your AKC or similar reputable registry for country, only two here in USA pretty much, not a 'paper' or pet registry and those can mean just the opposite, papers and pedigree to show and verify lineage.
www.pugs.org www.ukcdogs.com www.wildheirlabradorrescue.org  
www.dogfoodanalysis.com  
www.bornfreeusa.org