A person is eligible to file in an international patent application if he/she is a native or resident of a PCT Contracting State. Also, India is a contracting state for PCT. Hence, any Indian native/resident can file an international patent application under PCT. An application may comprise of several applicants. In those scenarios, only one of those applicants needs to fulfill the requirements.
In case none of the applicants is a resident of India then they can hire a patent agent for the filing process. However, we are talking about the PCT here. Hence, instead of starting their filing in India, they can simply first file an application in their native country and then enter India through the PCT National Phase.
Also, do make sure that you check out this free e-book: A Quick Guide to Patents. It deals with basics of patent procedures.
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