Format
Ten alphanumeric characters: AAAAA1111A. Case-insensitive but written uppercase.
Who has one
Any Indian tax resident with taxable income or who holds an Indian bank account. For an India-resident founder of a US LLC, PAN is almost always already in place.
Where it goes on Form 5472
In the owner section, as the foreign tax identification number. The 5472 instructions ask for a “US TIN, if any” (most India-resident founders have none) and the “foreign TIN”. PAN fits the latter.
PAN vs Aadhaar
Different numbers for different purposes. Aadhaar is a 12-digit Indian national ID — identity, not tax. The IRS wants PAN, not Aadhaar.
Schedule FA
On your Indian ITR-2 or ITR-3, you disclose the US LLC and any related foreign accounts on Schedule FA. The disclosure sits on the Indian side; the US 5472 and the Indian Schedule FA are independent filings that describe the same LLC — consistency across them matters.