Changing Creation Date of a PDF file

Changing Creation Date of a PDF file

Could you please let me know how I can change the creation date of a file
in Lion. I realise there is the touch-t command but that does not work in
Lion. A couple of people have mentioned another way, but I think they've
written the solution in "coder" language rather than layman language -
would someone be able to answer it in a way a layman can execute?
Many thanks for your help.