How do I protect a PDF document with a password that varies from one opening device to another?

Question

I'm a creative writer and I sell my works online. Normally, I would save a finished product into a PDF file, which I would protect by setting a password for it. However, I found that some bad actors first bought a work from me and obtained the password. They then went on to sell this work at a lower price without my authorization. Since I already told the password to the bad actors, they would pass it on to new buyers. I am suffering a loss from their actions.

I come to this forum to see if there is a way to set a PDF password that varies from one opening device to another. For example, the new buyers will not be able to use the password given by the bad actors on devices of the former.

Answer 1

Forget it.

What you're asking for is a DRM. Hollywood has spent fortunes on this, even including it in physical hardware.

It hasn't worked. There's not one series that's not available pirated. If someone wants to pirate your work, they can. HDCP, mentioned above, can be stripped with a 20$-box from eBay.

So you provide bad actors with a secured PDF. What stops them from extracting the decrypted content on their computer, and distributing the extracted content? Nothing.

Heck, they can even screenshot it and create a new PDF from the pictures.

Encrypting the PDFs is inconvenient to your customers, and places legitimate customers at the risk of losing access to the material they bought. It does nothing to deter someone from copying it, if they are determined to copy it.

Answer 2

If you give someone a document to view on his devices, that person also has to power to distribute it.

This is simply not something you can prevent, though entire industries have doomed themselves trying to accomplish something at least close to it. Repeatedly acting surprised when the money that went into it accomplished nothing in the long run.

However, if your regularly receive money in exchange for documents and your customer group is rather static: there are tools to give each customer a slightly different version of the document. You can then decide to stop selling to customers whose version ends up being shared beyond your intended audience.