You can do anything illegally but you also have to be ready for the consequences. Obtaining a PAN using forged documents has just a 10000 rupee penalty but obtaining Aadhaar card illegally will put you in prison for 3 years. Those who are obtaining Aadhaar illegally are setting themselves up for even greater trouble as their biometrics is forever stored with the GoI. Illegal immigrants will have to think twice before going down that route as once discovered will completely block their ability to legally enter India ever again (apart from a lengthy jail term and subsequent deportation).

1. http://www.thehindu.com/news/cities/bangalore/illegal-bangla...

2. http://www.tribuneindia.com/mobi/news/jammu-kashmir/communit...

3. https://m.indiatimes.com/news/india/here-is-why-you-should-n...