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I'm trying to sell a PDF file. I'm going to burn it and sell it on a CD locally. My fear is that one of the buyers will upload it online and make it available for free to the others. I was wondering if there's a way to make that uploaded file unable to open when someone downloads it. I'd like that copy I sold to be restricted to that one customer. I'm assuming the only way to do that is to restrict it to one computer, since it's impossible to restrict it to a person per se. So then how do I restrict it to one computer?

Even if I give a different password for each copy, the person who uploaded it could still post the password for that copy. So is there a free way to restrict it to one computer, workable on both PC or mac?

PS.These customers are not very tech savvy(but maybe enough to know how to upload a file and password). And the information in the PDF is somewhat time-perishable, meaning that maybe after a year it will be worthless. So I don't really need methods that are too aggressive/hard.

Artjom B.
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hel here
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  • i don't think it's possible. Even if it's possible, they can still print to pdf and generate a new pdf file. – ysrb Jul 13 '11 at 12:16
  • "they can still print to pdf and generate a new pdf file" true, but that takes being tech savvy, which these guys are not, so that specifically is not a problem. Thanks though. – hel here Jul 13 '11 at 12:19
  • If you have a Mac, all it takes it to click Print -> PDF – Simeon Jul 13 '11 at 13:20
  • FYI - you can turn off the ability to print a PDF at the time you create it. – plinth Jul 13 '11 at 20:42
  • @plinth: Not all PDF readers care about that – Simeon Jul 13 '11 at 20:56

3 Answers3

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Idiot Security

Send out the CD with a password that is equal to their personal/social security number and/or their e-mail address. This might make them not want to provide the credentials to the WWW. I'm now presuming they're dumb enough to think protected PDF:s are secure, and that they're concerned about privacy.

n00b Hacker Security

Provide the PDF inside of a custom format reader that has no export abilities and embed the PDF in your custom format within the executable. Use an obfuscator to further obstruct the decompiling process.

Average Impatient Hacker Security

Provide an external physical device that has a unique algorithm on it, responding differently to various inputs (common for internet bank security solutions). Require internet access to the material in an SWF or Java Applet using the techniques in "n00b Hacker Security", where you use the user credentials and the physical device's response to confirm that the algorithm matches that which you've sent to the particular user.

Skilled Patient Hacker Security

This is out of my league. And even if it wasn't, any suggestions here can be hacked too.

Simeon
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You can watermark it with customers name, phone number, address. This is called "social DRM". Customer would not want to share his information to public. Of course, PDF can be edited, but anything reasonable sophisticated can be cracked. You can also try to hide some unique information inside PDF, so customer might miss it while removing visible information.

Ondrej Galbavý
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After significant research, I have come to the conclusion that if you are selling a PDF document, it is best to just partner with a specialized company that can distribute it for you securely for a price and/or share of the profits. For example, SENDOWL will stamp your PDF documents before distribution and their cost is $15/month. There are other even more expensive solutions with much heavier security.

Locklizard for example allows you to:

-limit viewing and printing -limit modifying and copying -limit saving and sharing -prevent printing to file -prevent screenshots -you can decide when a document can no longer be viewed on the PC -can limit PDF documents to specific PCs -etc. etc. etc.

shreyasm-dev
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Agostinho Domingos
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