add unremovable watermark to a pdf

Hi guys
I have some pdf books that got them really difficult.
There are some programs in the net that can remove watermarks of the pdf books
But i want to know that is there anyway to add a watermark that no one can remove it?

Try Nuance Software

I would try to use "Nuance PDF Create" or their "PDF Converter" (last one also is available as a trial version). Both offer the option to watermark pdfs and both are used for business, so I presume the watermarks will be "unremovable". Besides the PDF Converter offers some really nice features when editing PDFs.
Link is: PDF Create - Nuance PDF Create 8 - PDF Files - Nuance.co.uk

Add Watermark in Multiple PDF Files

Yes there is a way by which you can add PDF watermark easily. You will get two types watermark options which are follows :

• Text Watermark :huh:
• Image Watermark

For more information you can go for this link SysTools PDF Watermark Software