Stamp the existing pdf file and save it again

I want to stamp first page of any existing pdf file with any text enter by the user and save it again or overwrite the file. I found some article about it on google but all are either create a new pdf file or save the stamped file in new pdf file. I want to save 开发者_开发技巧the stamping in existing file.

Have you any suggestions or source code.

Thanks in advance

Dinesh Kumar

Check out iTextSharp

You can manipulate PDFs with it.