What documents does a Pakistani national green card holder need when re-entering the United States?
All you need is your green card, but if you plan to be away for more than one year, you should get a reentry permit. If you don't get a reentry permit in that case, you may need a returning resident visa.
There are also legal implications if you stay away for more than six months.
Assuming your trip is shorter than six months, you should present your green card at the border. If you have them, you should also present other forms of identification, such as your passport, but that is not necessary. See https://www.uscis.gov/green-card/after-green-card-granted/international-travel-permanent-resident:
What documents do I need to present to reenter the United States?
If seeking to enter the United States after temporary travel abroad, you will need to present a valid, unexpired “green card” (Form I-551, Permanent Resident Card). When arriving at a port of entry, a U.S. Customs and Border Protection Officer will review your permanent resident card and any other identity documents you present, such as a passport, foreign national I.D. card or U.S. Driver’s License, and determine if you can enter the United States. For information pertaining to entry into the United States, see U.S. Customs and Border Protection’s webpage.
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