Now you can link your aadhar number with that of PAN card. This is done by sending an SMS to either 567678 or 56161. First type UIDPAN then your 12 digit Aadhar number followed by your PAN number – send it to 567678 or 56161. Format is as follows:
UIDPAN 012345678910 abcdefghij
( where 012345678910 is the aadhar number and abcdefghij is the PAN number )
Alternatively you can do this online from this page from Income Tax Department
More more information visit Incometax of India’s website