How to add mobile number in pan card?

You'll need to apply for a "Change/Correction in PAN Data" to get this done.

It’s a fairly simple process online. You can visit either the Protean (formerly NSDL) or the UTIITSL website. On the site, look for the online application for "Changes or Correction in PAN." Fill out the form with your existing PAN number. You’ll find a specific field for your mobile number and email under the communication details section.

The easiest way to verify your identity is through Aadhaar-based e-KYC. An OTP will be sent to the phone number linked with your Aadhaar. There's a small processing fee. Once you submit and it’s approved, your new mobile number will be updated in the database.