I'm wondering what the capabilities for document (PDF/DOCX/XLSX/PPTX) tracking are , specifically to determine whether a client has broken a non-disclosure agreement.

Here's a scenario:

  • Service provider has confidential documents which can be released under NDA
  • Client requests these documents, signs NDA
  • Client then alters documents somewhat (possibly by way of rebranding) and stores internally for their use

Is there any technical way for the service provider to track whether their documents have been altered such as a beacon?

Edit: Had some constructive feedback here regarding the question being rather broad. To focus the scope, I'd be keen to understand the actual techniques for one of the noted document filetypes if possible (i.e, How do you track changes made to a remote PDF file you have created?)

  • 2
    The client could print and scan the document, thus breaking any digital tracking you might have added to the document. Sep 24, 2018 at 11:07
  • As is I think that this is far too broad. The way you would track a document will vary wildly depending on the type of document in question, be it PDF, Excel, Word, Images, etc... I think this is a good question generally but too broad as-is. Sep 24, 2018 at 13:26

2 Answers 2


There's no way to really protect any document against this kind of leak. As soon as anyone have a copy of the document, it can be altered in order to remove the protections:

  • print and scan
  • change format: pdf to text, or doc to text, or anything to image
  • copy and paste

Those operations can be done on an offline computer, so any beacon have no chance of working.

  • I don't think this answer is entirely fair. Yes, any digital protections can be circumvented. However, that doesn't mean that a given leaker is either aware of how to do such a thing, aware of how to break a particular safeguard, or even aware that a document may be hiding secret tracking systems. As a result, were my CD important enough, I would absolutely embed whatever tracking mechanisms I could, and as many as I can. Sep 24, 2018 at 13:28
  • As a counter example with your print and scan option, most printers embed invisible (to the human eye) watermarks in documents which can potentially survive a print and scan. These can't actively broadcast their presence during leaking, but our government has almost certainly used them to track down the source of leaks previously: washingtontimes.com/news/2017/jun/6/… Sep 24, 2018 at 13:29
  • ^ I'm sure that's how Reality Leigh Winner was caught by the NSA!
    – Doomgoose
    Sep 24, 2018 at 13:36
  • Print it on a dot-matrix printer, I don't think any invisible watermark would survive.
    – ThoriumBR
    Sep 24, 2018 at 20:28

As mentioned in the other answers, there is no digital way to be absolutely sure that a document won't be copied, edited, or transferred in some way using digital means.

You could add a layer of protection like loading a remote image in your PDF with an identifier of that particular client in the URL, which would help you know when that PDF is loaded. Continued use from different IPs might signal the document was copied by this client and released improperly.

However, measures like this can be circumvented if the client knows what to look for. You will always be susceptible to someone copying the data in an offline way (taking a photo, printing and re-scanning), or removing metadata digitally (reprinting the PDF digitally to remove metadata).

In the end it is a game of setting up reasonable safeguards to catch casual offenders and setting up other policies to protect from determined leakers.

It is a bit tangential to your question, but if you are interested in a less digital solution you may want to consider implementing a Canary of some kind to help track down a leak after the fact. Since these rely on more human factors it may be less likely for them to be noticed. This is called a Canary trap (https://en.wikipedia.org/wiki/Canary_trap), and is when you give a different variation of the document to each signer of an NDA, so that when information is leaked you can use these variations to determine who leaked the data.

These should be small to prevent it from being noticed, but if recipients of different document versions are unlikely to compare the data, it gives you the possibility for recourse in case of a leak.

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