I can imagine it being a pain in the ass to spend a lot of time and effort creating an ebook, just to have some bastard leak it to bittorrent or wherever a few weeks later. This idea dawned on me a few weeks ago on how to find those people responsible for it. Putting an obvious order # or serial number (unique for each customer) on the book has limited use, all that is needed to cloak their identity is to delete those few lines of text in the pdf. In order to successfully plant an identifying mark in the ebook, you must conceal your intentions..... What we need to do is hide various numbers or keywords or other markings that identify the customer in plain sight. Let me list a few examples. Lets say there is a paragraph saying "It does not matter if you make $4.00, or $4200 every day, I guarantee you will double your profits after reading this book!" That sentence looks harmless enough....right? Now imagine changing that $4200 to $4300, or $4100. By those slight changes in each copy of the ebook you give to people, you can determine who has what copy, which is obviously great if someone leaks your book, then you can easily press charges against them (or blackmail, OR now you know where they live, whatever floats your boat ). The great thing about this concept is that there are so many small variations you can do to your ebook, there is little people can do to detect what you are doing. Here are a few ideas that come to mind. -Lets say you finish a sentence somewhere like this...... Count the number of periods you have. -Go get a thesaurus and change a few adjectives. The ridiculous profits are now ludicrous profits, the draconian CPA network is now the strict CPA network. The possibilities for this are endless. -In any tables you have, lets say screenshots of payouts, edit the page and change all the dates. Additionally, you can put small variations on your payouts. $458.43 becomes $458.45, and so on and so forth. -Have interchangeable words. Instead of working to get that red Ferrari, now it is a red BMW, or a yellow Porsche, or a Black Bentley... Your shoe color, what you spent with your money, the kind of computer you use, ANYTHING really. -If you ever name any locations (lets say where you grew up, or where used to live) can be changed. Los Angeles, Denver, or Phoenix can all be used to mark the book. -Even "typos" can be used. Use at your own risk though, you don't want to have your product looking like shit. -Any important pictures you have can slight variations on them. What does your mouse look like in the screenshot? What theme are you using on your computer? What is the URL in the browser? What tabs do you have open, and what do they say? WHAT TIME IS IT? If people stealing these books begin to realize what people are beginning to do, they may delete the unimportant paragraphs (thinking they have markings in it), so it is important to think one step ahead, and put these markings inside the actual meat of your ebook, the information that is most valuable. So small variations on your profits (or expenses), or changing a few offers you used, or even how many hours you work a day (or used to). Any combination of the above methods can be used, either to have your marking information spread somewhere to less suspicious (black Bentley Los Angeles is customer X, red BMW NYC is customer Y), or for redundancy purposes. I am sure it can get way more complex than this, if you are creative you can probably think of much more clever ways to hide things. Seriously, be creative here, the possibilities are endless for protecting your product. And speaking of ebooks, no one better turn this idea into one!