17

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}?

|improve this question

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

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • 14
    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
  • 5
    Render the text as a picture. – Andrey Vihrov May 18 '11 at 22:23
  • 2
    Of course, preventing Ctrl-C doesn't protect against OCR. – Dean Serenevy May 19 '11 at 16:13
  • 1
    I think this has its uses. For example when distributing a PDF with lots of personal info. (Say a kind of address book.) The PDF goes to a large group of people. If by chance it ends up on the internet, then crawlers and bots can't (easily) read the PDF. From a privacy perspective, I think this a good. – jmc Apr 21 '15 at 19:19
12

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.

|improve this answer

Not the answer you're looking for? Browse other questions tagged or ask your own question.