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Old September 14th, 2004, 02:44 PM
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Default How to create a Read-Only PDF in C#.NET?

Greetings p2p,

Here is my problem: my boss wants to create a PDF file for our clients that they can open (without entering a password) that cannot be viewed or modified programmatically. This file may be passed on to our clients' clients, and while we want everyone to be able to reuse (or "re-view") the contents, we want to make it as difficult as possible to programatically reuse the contents (as there are IP issues involved).

I have looked at encrypting the PDF, but this appears to require a password everytime the file is used. This, unfortunately, does not work for our situation. I know that PDFs have two levels of encryption: one for general viewing and one for modification. Putting a password on modification and not general viewing does not solve our problem either.

Any ideas as to how this could be achieved (or not)?



Old September 15th, 2004, 08:52 AM
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I can't say I am clear as to what the problem is- A PDF can be "annotated" but not changed. by default. If your concern is someone will read the PDF into another file and modify it- the modified file will show the signs of change (EG: A different date). If you encypt it, of course, it can be un-encrypted and then changed.

I don't know if there's a way to prevent a programatic attack on an PDF other than encryption- and that's not foolproof.

the other idea is to digitally sign (but not encrypt) the file. If the file is changed, the signature will drop out. A CRC check could also show changes in the file.

Hal Levy
Web Developer, PDI Inc.

NOT a Wiley/Wrox Employee

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