# Is it possible to produce a PDF with un-copyable text?

Is it possible to produce a PDF with un-copyable text? I mean, when you want to copy text from the PDF, you can't copy it or what you copy is nonsense characters.

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Is it possible? Yes. (Well, sort of -- you could always convert to an image and OCR.) Is it a good idea? No. We must push back against the forces of OCR and commercialism, and push for the causes of open access, searchability, and software freedom. If those who favor open source software don't, no one will. –  frabjous Feb 17 '11 at 15:16
IMHO, it is never a good idea to prevent other people from copying texts in a PDF file through techniques. If we must do such things, don't convert the texts to a image (vector or bitmap). Besides loss of quality, the result file may be very large. –  Leo Liu Feb 17 '11 at 15:39
In addition, you'll do a huge disservice to blind people (though I guess PDF's aren't very accessible even in the best of cases). –  Caramdir Feb 17 '11 at 15:52
"Cracked" isn't the right word. OCR = Optical Character Recognition. It takes an image, analyzes it to try to recognize letter shapes, and then outputs text. Of course, they could always retype what you've written, but that's usually faster. –  frabjous Feb 19 '11 at 20:12
@warem: No, it's not possible. All you need to break it is a thing called "a typist". –  Brent.Longborough Jun 3 '11 at 21:23

Besides converting all texts to images, one method as I know, is to destroy the Cmaps of the fonts. We can use cmap package and a special cmap file for this purpose.

(Warning: it does not make much sence to produce un-copyable PDF. OCR is very easy today.)

% pdflatex is required
\documentclass{article}
\usepackage[resetfonts]{cmap}
\usepackage{fancyvrb}
\begin{VerbatimOut}{OT1.cmap}
%%DocumentNeededResources: ProcSet (CIDInit)
%%IncludeResource: ProcSet (CIDInit)
%%BeginResource: CMap (TeX-OT1-0)
%%Title: (TeX-OT1-0 TeX OT1 0)
%%Version: 1.000
/CIDInit /ProcSet findresource begin
12 dict begin
begincmap
/CIDSystemInfo
<< /Registry (TeX)
/Ordering (OT1)
/Supplement 0
>> def
/CMapName /TeX-OT1-0 def
/CMapType 2 def
1 begincodespacerange
<00> <7F>
endcodespacerange
8 beginbfrange
<00> <01> <0000>
<09> <0A> <0000>
<23> <26> <0000>
<28> <3B> <0000>
<3F> <5B> <0000>
<5D> <5E> <0000>
<61> <7A> <0000>
<7B> <7C> <0000>
endbfrange
40 beginbfchar
<02> <0000>
<03> <0000>
<04> <0000>
<05> <0000>
<06> <0000>
<07> <0000>
<08> <0000>
<0B> <0000>
<0C> <0000>
<0D> <0000>
<0E> <0000>
<0F> <0000>
<10> <0000>
<11> <0000>
<12> <0000>
<13> <0000>
<14> <0000>
<15> <0000>
<16> <0000>
<17> <0000>
<18> <0000>
<19> <0000>
<1A> <0000>
<1B> <0000>
<1C> <0000>
<1D> <0000>
<1E> <0000>
<1F> <0000>
<21> <0000>
<22> <0000>
<27> <0000>
<3C> <0000>
<3D> <0000>
<3E> <0000>
<5C> <0000>
<5F> <0000>
<60> <0000>
<7D> <0000>
<7E> <0000>
<7F> <0000>
endbfchar
endcmap
CMapName currentdict /CMap defineresource pop
end
end
%%EndResource
%%EOF
\end{VerbatimOut}

\usepackage{lipsum}

\begin{document}

\lipsum

\end{document}

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your method worked. thank you. but if i change \documentclass{article} to \documentclass[titlepage,a4paper,12pt]{article}, it didn't work. –  warem Feb 18 '11 at 2:33
i just found if i didn't define 12pt at the beginning, then defined a newcommand to set the default font size later, your method worked now. i don't why. on the other hand, your method works for the whole text, is it possible to just work part of text? –  warem Feb 18 '11 at 3:15
resetfonts doesn't work for 12pt. You can follow cmap.sty to undefine more predefined fonts. I have no much time. –  Leo Liu Feb 18 '11 at 5:48
That method does not work me. My evince allows me happily to copy and paste the text. Also pdftotext extracts all the available text. So this method does not work. –  Frederick Nord Feb 14 '13 at 20:51
For me too, this solution don't work. –  dexterdev Apr 16 at 8:20

You can disable the copying of text with the help of PDF encryption. With it you can also disable other things like printing.

You need to use an external PDF tool like pdftk or of course the full version of Adobe Acrobat to encrypt the PDF.

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However, encryption doesn't work for (almost all as I know) non-Adobe PDF readers. –  Leo Liu Feb 17 '11 at 15:14
I often use a certain open-source reader (with just one line of code commented out) to bypass PDF protection and passwords. Anyone familiar with SourceForge, GIT and MAKE can easily roll their own in a matter of minutes too. –  Mark K Cowan Aug 12 '13 at 23:54
@MarkKCowan I know of other, less sophisticated (if but also effective) ways than what you describe; out of sheer curiousity (though that curiousity is not that large that I'd try and patch it myself): Could you provide more verbose details or a link to a commented (indicating the commented-out line) GIT ? - sry about the overuse of (brackets); I'm drunk. –  nutty about natty Aug 14 '13 at 20:22
It was a long time ago when I built it. I think it was a Java application, there was one particular line which was a const "final boolean <something> = <somevalue>;" which related to password protection. Apparently, Ubuntu was the only distro where the password protection had been enabled, so I flipped that boolean and recompiled to produce a binary which didn't bother with the whole password fake-DRM stuff. Strictly speaking, I changed the value of a boolean constant, rather than commenting out a line. –  Mark K Cowan Aug 14 '13 at 23:27
Okular has a user setting which determines whether it recognises DRM or not... –  cfr Aug 25 '14 at 3:39

# Remarks

I use a little script, which converts all my fonts to paths. The script uses the first parameter as input of a .pdf-file and writes the output to a file with the same name and the extension-rst.pdf

You need Ghostscript for my script to run.

# Implementation

Runs on bash

#!/bin/sh

GS=/usr/bin/gs

$GS -sDEVICE=pswrite -dNOCACHE -sOutputFile=- -q -dBATCH -dNOPAUSE "$1"       -c quit | ps2pdf - > "${1%%.*}-rst.pdf" if [$? -eq 0 ]; then
echo "Output written to \${1%%.*}-rst.pdf"
else
echo "There were errors. See the output."
fi


use ps2write (in stead of pswrite) these days as seen here.

# Result

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No match for OCR though :D –  Mark K Cowan Aug 12 '13 at 17:54
Well I guess, that there is no way to trick any OCR Software (without adding things, like striking/crossing the text out), because the OCR Software can read, what you can read. –  Henri Menke Aug 12 '13 at 20:50
Specialised OCR software can break some types of CAPTCHA too... You can use excessive striking/deforming/noise to harden your file against this, but then humans won't be able to read half of it either! –  Mark K Cowan Aug 12 '13 at 23:52
Your script works, but (at least on my files, which are slides produced with beamer) produces very pale and large files. It also takes a relatively long time to finish. –  Anthony Labarre Oct 22 '13 at 8:46
@Trickster You run it like bash script_name "path/to/pdf/file". You don't need sudo as no additional privileges are needed for this script. –  Henri Menke Nov 24 '13 at 9:30

Luatex allows manipulating fonts in the define_font callback. Luaotfload facilitates this even more with an extra hook it installs right after the font loader has finished its job: the luaotfload.patch_font callback. Normally it is used for serious and constructive tasks like setting a couple font dimensions or ensuring backward compatibility in the data structures. Of course, it can also be abused for dirty hacks like disabling copy and paste.

At the point where the patch_font callback is applied, the font is already defined and ready to use. All necessary tables are created and put in a place where Luatex expects them. Among these is the characters table that holds preprocessed information about the glyphs. In the below code we modify the tounicode field of each glyph so that it maps to some random location within the printable ASCII range. Note that this does not affect the shape and metrics of the glyph since those are unrelated to the actual codepoint. As a consequence, the PDF will contain legible text that cannot be copied.

Package file obfuscate.lua:

packagedata = packagedata or { }

local mathrandom    = math.random
local stringformat  = string.format

--- this is the callback by means of which we will obfuscate
--- the tounicode values so they map to random characters of
--- the printable ascii range (between 0x21 / 33 and 0x7e / 126)

local obfuscate = function (tfmdata, _specification)
if not tfmdata or type (tfmdata) ~= "table" then
return
end

local characters = tfmdata.characters
if characters then
for codepoint, char in next, characters do
char.tounicode = stringformat ([[%0.4X]], mathrandom (0x21, 0x7e))
end
end
end

--- we also need some functions to toggle the callback activation so
--- we can obfuscate fonts selectively

local active = false

packagedata.obfuscate_begin = function ()
if not active then
"user.obfuscate_font", 1)
active = true
end
end

packagedata.obfuscate_end = function ()
if active then
"user.obfuscate_font")
active = false
end
end


Usage demonstration:

%% we will need these packages
\input luatexbase.sty

%% for inspecting the pdf with an ordinary editor
\pdfcompresslevel0
\pdfobjcompresslevel0

\RequireLuaModule {obfuscate}

%% convenience macro
\def \packagecmd #1{\directlua {packagedata.#1}}

%% the obfuscate environment, mapping to Lua functions that enable and
%% disable tounicode obfuscation
\def \beginobfuscate {\packagecmd {obfuscate_begin ()}}
\def \endobfuscate   {\packagecmd {obfuscate_end   ()}}

%%···································································%%
%% Demo
%%···································································%%

%% firstly, load some fonts. within the “obfuscate” environment all
%% fonts will get their cmaps scrambled ...

\beginobfuscate

\font \mainfont   = "file:Iwona-Regular.otf:mode=base"
\font \italicfont = "file:Iwona-Italic.otf:mode=base"

\endobfuscate

%% ... while fonts defined outside will have the mapping intact

\font \boldfont       = "file:Iwona-Bold.otf:mode=base"
\font \bolditalicfont = "file:Iwona-BoldItalic.otf:mode=base"

%% now we can use them in our document like any ordinary font

\mainfont
obfuscated text before {\italicfont     obfuscated too} and after \par
obfuscated text before {\boldfont       not obfuscated} and after \par
obfuscated text before {\bolditalicfont not obfuscated} and after \par

\bye


Result in PDF viewer:

Contrast this with the output of pdftotext:

\rf2yC'I_J I_dI r_f\{_ 9;Hbp<<L& <99 '5J 'fI_{
\rf2yC'I_J I_dI r_f\{_ not obfuscated '5J 'fI_{
\rf2yC'I_J I_dI r_f\{_ not obfuscated '5J 'fI_{


EDIT Because the generous karma donor specifically asked for a Context solution, I’ll throw that one in as a bonus. It is a good deal more elegant since it relies on the font goodies mechanism that allows applying postprocessors to specific fonts which can afterwards be used just like common font features.

\startluacode

local mathrandom    = math.random
local stringformat  = string.format

--- create a postprocessor

local obfuscate = function (tfmdata)
fonts.goodies.registerpostprocessor (tfmdata, function (tfmdata)
if not tfmdata or type (tfmdata) ~= "table" then
return
end

local characters = tfmdata.characters
if characters then
for codepoint, char in next, characters do
char.tounicode = stringformat ([[%0.4X]], mathrandom (0x21, 0x7e))
end
end
end)
end

--- now register as a font feature

fonts.handlers.otf.features.register {
name         = "obfuscate",
description  = "treat the reader like a piece of garbage",
default      = false,
initializers = {
base     = obfuscate,
node     = obfuscate,
}
}

\stopluacode

%%···································································%%
%% demonstration
%%···································································%%

%% we can now treat the obfuscation postprocessor like any other
%% font feature

\definefontfeature [obfuscate] [obfuscate=yes]

\definefont [mainfont]   [file:Iwona-Regular.otf*obfuscate]
\definefont [italicfont] [file:Iwona-Italic.otf*obfuscate]

\definefont [boldfont]       [file:Iwona-Bold.otf]
\definefont [bolditalicfont] [file:Iwona-BoldItalic.otf]

\starttext

\mainfont
obfuscated text before {\italicfont     obfuscated too} and after \par
obfuscated text before {\boldfont       not obfuscated} and after \par
obfuscated text before {\bolditalicfont not obfuscated} and after \par

\stoptext

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I'll see your obfuscator and raise you by some free OCR package :D –  Mark K Cowan Nov 6 '13 at 15:20
@Mark Never mind OCR, this is deterministic 1 to 1 character mapping: t=I, e=_, x=d, etc. A few minutes with a document could produce a sed substitution expression for all the changed glyphs. Pipe your pdftotext into that and you have a 100% fix. All this does is waste both author (and reader) time without actually solving anything but making them feel like they have. Poor-mans-DRM is even worse than the real thing. –  Caleb Dec 20 '14 at 15:49

If content can be viewed, it can be copied. No matter what encryption and restrictions are used, at some point the content must be put out in plain view in order for it to be of any use. This is probably true of all digital content and most physical content larger than the nanoscale...

For example, a PDF:

• Rasterisation: Printscreen => OCR
• Any protection: Re-type it out
• Content protection: Modified build of an open-source reader

Web content:

• Right-click popup: Opera=>Prevent page receiving content menu events
• Right-click popup: "Menu" button on any modern keyboard
• View page source, use Chrome/Opera/Firefox debugger to get URL of desired content

Audio (e.g. HDCP):

• Headphones socket on TV => line-in socket on PC
• Solder to tap into preamplifier => line-in socket on PC

Video (e.g. HDCP):

• Many, many options... A quick google search will show you.

Encrypted content on someone's laptop/pendrive:

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One of these is not like the others. The last item is both wrong and a different scenario from your premise. –  Caleb Dec 20 '14 at 15:54

The answer is: Yes. There is a way described here: http://spivey.oriel.ox.ac.uk/corner/Obfuscated_PDF

But it looks tedious and doesn't use pdflatex. The method, however, is described as being portable to PDF. It involves changing glyphs of a font and other dirty things that get you bad dreams.

I didn't find a method described for directly PDF let alone something automated for pdflatex. I'll happily buy you a beverage of your choice if you implement it :-)

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Use XeTeX to at least get some "nonsense characters", see here and here.

Though this would obviously be just a nuisance for most cases/users (which can be avoided using LuaLaTeX instead), depending on what you are trying to achieve compiling with XeTeX` may prove to add at least some value to your solution...

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