Add text to a PDF

[oddball508]

Does anyone know of a commandline or vbscript way of adding text to a PDF file without regenerating the PDF file?

Basicaly I have a large number of PDF files (around 1.3 million). I want to add a serial number to the bottom right hand corner. I can not use a watermarking process such as in PDFTK as the originals PDF file are created from images (ie One image per page and that image fills each page).

Thanks.