[Tex/LaTex] Protect text in PDF from being copied

copy/pastedrmpdf

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}?

Best Answer

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.

Related Solutions

[Tex/LaTex] How to make listings code correct copyable from PDF and with hyperlink

You can mark the line numbers so that they are not copied, i.e. an empty text is copied instead, using the technique described in Is it possible to provide alternative text to use when copying text from the PDF?. The required code can be added using the numberstyle option if listings, as shown below. If you want to add other formatting macros to the numbers either add it before the \noncopynumber macro or inside of it.

The solution for the spaces you found in How to make listings code indentation remain unchanged when copied from PDF? should be PDF viewer independent. I don't see any reason why different PDF viewers should display it differently. Once the spaces are frozen to the PDF the presentation should be identical with all viewers. That's the basic idea behind the PDF standard.

Copying the text to the clipboard might be possible using some JavaScript but would not be that trivial to add. I would attach the listings also as files to the PDF and provide a link to that instead (as already suggested by others in the comments).

\documentclass{scrbook}
\usepackage{xcolor}
\usepackage{accsupp}

\usepackage{listings}

\lstdefinestyle{demostyle}{
    basicstyle=\small\ttfamily,
    numbers=left,
    stepnumber=1,
    frame=single,
    columns=flexible,
    keepspaces=true,
    numberstyle=\noncopynumber
}

\newcommand{\noncopynumber}[1]{%
    \BeginAccSupp{method=escape,ActualText={}}%
    #1%
    \EndAccSupp{}%
}

\makeatletter
\def\lst@outputspace{{\ifx\lst@bkgcolor\empty\color{white}\else\lst@bkgcolor\fi\lst@visiblespace}}
\makeatother

\begin{document}
\begin{lstlisting}[style=demostyle]
\textbf{\textit{foobar}}
\textit{\sffamily foobar}}
\end{lstlisting}
\end{document}

Using this I get the following when copying the text:

\textbf{\textit{foobar}}
\textit{\sffamily foobar}}

For longer text, e.g. multiple pages long, you will have issues with the footer and header. These could be made un-copyable using the same technique. Attaching the listings as files would be a good alternative here.

[Tex/LaTex] Remove hyphen from word spanning two lines in text copied from a pdf file

Worst case scenario, the PDF has the hyphens at the end of the line rendered as the same hyphen that sits between words, let's call them 'line break' and 'interword' hyphens for now.

That would mean they are indistinguishable automatically (an interword hyphen might coincide with a line break; impossible to detect). In which case, search & replace (with nothing) to get rid of all of them, then S&R for words that are now known to miss a hyphen. Sorry.

Better case scenario is that the actual characters inside the PDF are different, even though they might look the same. Copying & pasting, depending on your PDF reader, tends to lose that distinction, if it was there in the first place. Same issue makes for 'end of line' (EOL) characters for every visible line in the PDF, rather than one at the end of a paragraph. LaTeX doesn't mind (it looks for empty lines) but your other text editing needs or tooling might.

On the assumption you have been copying&pasting, you might be able to get more results to work with by extracting the text from the PDF automatically. Google for 'PDF to text'; there are a number of options available, from Windows GUI tools, to OS X builtin PDF handling (look into Automator) to command line tooling for UNIX/Linux/Cygwin environments.

The output would be plain text. Some tools perform or allow for some manipulation of the extracted text, preserving only actual line endings rather than merely the ones shown, etc.

For text manipulation perse, the typical command line tools in a UNIX environment would be able to get the bulk of your issues out of the way. That may or may not be useable advice to you, but I would reach for Vim, sed and a sprinkling of regular expressions all wrapped in some Bash.

Best Answer

Related Solutions

[Tex/LaTex] How to make listings code correct copyable from PDF and with hyperlink

[Tex/LaTex] Remove hyphen from word spanning two lines in text copied from a pdf file

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