Visible watermark (ex libris) on Mobi files - watermark

Question

We have a client selling ebooks and he wants to add the buyer's name on every page of the book (for example in the footer) so that it discourages him to share it too widely. Apparently this is called adding an "ex libris". Our client wants to sell ebooks in PDF/ePub/Mobi formats.
I've searched the Interweb about how to do this and so far I've found that doing this to PDFs is quite easy, that there is a library to do exactly this on ePubs. But I've found close to nothing related to mobi files.
So my questions are :
Is it possible to add text on every page of a given .mobi file, for example in the footer?
If it's not possible, how accurate would it be to convert a watermarked epub to the mobi format? What would be the best tools and practices for the job?
This discussion is not about how I could add a hidden watermark to the files through some form of steganography.

Answer 1

We have done something similar before to use a footer image at the bottom of each page in a Mobi file. This image could contain the name of the buyer.
<style>
body{
background-image:url('[watermarkpath].PNG');
background-repeat:no-repeat;
background-attachment:fixed;
background-position:center bottom;
background-size:contain;
}
</style>
I suggest making the image itself transparent so that it doesn't interfere with the text. Hope this helps!