Hi ishtiyaq.makda
I'm not with Laminar Research, just a fellow simmer in the UK, but the short answer is yes, you can have as many downloaded copies of X-Plane 11 as you wish.
But, if you start using more than one PC at a time whilst connected to the internet, you may find that LR revokes your licence without warning!
The basic rule is one licence per copy of X-Plane 11.
Regards