How to add header/footer to existing pdf file?

Hi,Support:
Is there any method to add header/footer to each page in existing pdf file?
I tried some demo codes in this forum, but I did not find how to set fontsize,fontname and fontcolor of the added header/footer.
How to work it out?
Thanks for your help!

@ducaisoft

Could you please share your sample PDF document along with code snippet that you have tried so far. Also, please share an expected output PDF as well. We will test the scenario in our environment and address it accordingly.