Re: PDF is blocked for printing, etc. OK for acroread (it behaves as expected), but KPDF allows me to print it, even if it is protected! Why?

[Stefan Monnier <monnier@iro.umontreal.ca>]

> My reason is quite complicated, and is really justified. Briefly, one
> person that I know needs to have some report I wrote, but this person
> should not be able neither to print it nor to extract content from it,
> for a simple reason: this person could transmit a part (or the whole)
> [of the] document to a third party, and this third party should not
> receive the report from the person who could send it to him (the third
> party), but the third party wants the other fellow (actually not a
> fellow to me) to receive the report.

Doing it via technical means requires that you be able to formally
define and control all the cases you want to rule out (and hopefully
leave the remaining cases possible).

Can you technically prevent him from passing the whole PDF to someone
else?  Can you prevent her from taking a photo of her screen?
Can you prevent her from printing his screen?  ...

Once you've solved the above technical problems, you'll have to solve
the remaining one: can she still read the document?

And to make it more interesting: assuming you can't prevent all of those
things from happening: what happens if she does one of them?
Assuming she hasn't actively tried to workaround the DRM (e.g. she
simply took a photo of the screen or transmitted the whole PDF
document), her act were perfectly legal so ... what would happen?

Now think about the other route: the one based on the law instead of
technology: the legal document can simply describe what she's allowed to
do, and that will automatically cover all imaginable ways to
circumvent any technological means you could imagine.  And if she does
break the contract, you can sue her.
Don't know about you, but to me, it sounds a lot more useful.


        Stefan