Open Source / White Label e-book solutions with DRM?

[jaagare]

I have been try to find across the web but not really successful in finding some Open Source or White Label e-book solution.

Here is my basic requirement:
Once a user purchases an ebook > the code should apply DRM to it in some format.
Then the user would have access to e-book reader for various devices like Windows, Andriod, iOS and desktop. Only users who have access to the ebook could read it and they would not be able to download and send it to someone else.

So is such a solution readily available? Because the prices quoted by some companies for just white labeling are as much as creating the entire application from scratch. Some also charge an additional per book fee or a monthly maintenance fee over and above their initial costing.

My initial thought has been to have the e-books in PDF format but is there some DRM available for PDF? Other than Adobe as I have heard it costs a lot of money. Second option would be ePub format but not sure if there are any readily available solutions for that. Last option I think and simplest would be to add the purchasers name / email / contact details as water mark which I believe is also the cheapest and more secure compared to other modes.

Any suggestions? Thanks for your help in advance!

[GSto]

If you want to watermark files, Gumroad can do that for you, as well as handling all of the payment processing.

[jaagare]

Thanks. That looks good but I think we need to subscribe to their monthly services. I was looking more for a white label solution which could integrate with say Woocommerce or any such plugin. Most of the services need monthly payments or the upfront costs are quite high. I was looking more of a one time payment kind of solution with some basic DRM in place which is generated at runtime.

Like I also mentioned in my opening post the last option I see is to watermark purchasers details to the PDF rather than using ePub as I have not found a white label solution for ePub files