Protect text in PDF from being copied [duplicate]

Possible Duplicate:
PDF with un-copyable text

What is the most effective ways to protect text in a PDF from being copied with Ctrl+C?

I know about standard PDF copy protection, and also know that it can be removed relatively easily. [BTW: Can this copy protection be added to a PDF directly from Latex?]

Inspired by "Is it possible to provide alternative text to use when copying text from the PDF?", I tried:

\documentclass{article}
\usepackage{blindtext}\usepackage{accsupp}

\begin{document}
\BeginAccSupp{method=escape,ActualText=}
\Blindtext[3][2]
\EndAccSupp{}
\end{document}


This appears to protect the first page in Adobe Reader 9 against simple copying. The second page is not protected anymore. Is it possible to extend the protection to the entire document? It also appears that all text remains accessible in Foxit Reader 4.3.

I imagine a very effective approach would be to add invisible garbage text after each few letters. This would increase the size of the PDF a bit but this would not be a problem.

Any ideas are much appreciated.

A powerful approach is redefining the Cmaps of the fonts, suggested in an answer to "PDF with un-copyable text". How can this approach be used together with non-standard fonts? E.g. such as Times loaded through package \usepackage{times} or \usepackage{mathptmx}?

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marked as duplicate by Leo Liu, Seamus, Alan Munn, Jukka Suomela, CaramdirMay 20 '11 at 16:22

Please, don't... –  Jukka Suomela May 18 '11 at 21:06
@Jukka: I agree, but would still like to discuss the options :-) –  Frank Seifert May 18 '11 at 21:24
Render the text as a picture. –  Andrey Vihrov May 18 '11 at 22:23
@Leo Liu: Redefining Cmaps appears to be a powerful method. Could you maybe give some guidance as to how to apply it for different fonts and font sizes. How do I find out the encoding of a font? –  Frank Seifert May 19 '11 at 11:58
Of course, preventing Ctrl-C doesn't protect against OCR. –  Dean Serenevy May 19 '11 at 16:13

The accsupp technique is not intended for longer text and it is no surprise that it is limited to one page. You would need to add it for every page somehow. This is a PDF 1.5 feature and viewer which do not support it will likely just display the original text. Therefore I would not rely on it. It is not indented to be used for this purpose anyway.
The normal PDF copy protection you mentioned requires encryption. The pdfcrypt package provides the needed options, but encryption support of pdftex was dropped since pdfTeX-1.10a (2003-01-16), so you are out of luck. However, the manual of this package lists several free alternative ways to add this security feature to PDFs.