I have spent past few days learning about type setting Urdu in Nastaleeq and few related issues. To my surprise the most commonly used pdf viewer evince does not render Urdu pdf documents. Okular renders it correctly, see following two images for a comparison.

Evince Okular
Urdu as rendered by evince Urdu as rendered by okular

A very useful resource for type setting Urdu in latex Abid Mujtaba’s github repo