Suppose I want to generate 100 apparently identical PDF files, where I hide some kind of key, in order to distribute them among 100 different people. Now I detect an online shared copy of the document and I need to track who of that 100 people uploaded it.  My first approach would be to compile them in some way (maybe ) to, for example, include among its hyperref PDF keywords some "UserNr001", "UserNr002", ... tags.  What I'm asking for is a more subtle way to mark a PDF from the .tex file.  Maybe related:  and .
I'd like to add an invisible watermark to each PDF document that I produce so that in case it leaks, I know where it leaked from. Anyone knows what would a good way for an invisible watermark be in a PDF document and how to add one?
I followed the beginner steps for creating a .  The child theme was created and it appears as an option on my Themes page. But unlike the other Themes on the page (including its parent), there is no preview.  The other themes ("Twenty Twelve," "Twenty Thirteen," and "Twenty Fourteen") are all listed with an image preview.  My child theme ("Twenty Fourteen Child") does not have any image. The child theme can be applied without issue.  This issue arises when I create child themes from other themes as well. Any ideas why this is happening and if I can resolve? I have a problem analysing this sentence from the point of finite/nonfinite clauses, clause elements and their functions:     He does not want to destroy his parents' dream of him achieving a Cambridge degree.   I am especially interested in the: dream of him achieving a Cambridge degree.  I know that 'achieving a Cambridge degree' is a non-finite -ing participle clause. However what is its function? And what is the function of 'of him'? Is it a postmodification? How can one differentiate between "who" and "whom"? Many times, I've been asked the difference between "who" and "whom". I myself know the difference, but it is hard to explain to others. What is the easiest way to explain it to those with a basic understanding of English? A mnemonic (if possible) would help. How to modify the space between the numbers and text of sectioning titles in the table of contents? I'm preparing a document using the book class. In the table of contents, the space between the subsection number and title is too wide. How to reduce it? Problem: Suppose $f$ is continuous for $x\ge 0$, differentiable for $x&gt;0$, $f(0)=0$, and $f'$ is monotonically increasing.  Define $g(x)=\frac{f(x)}{x}$ for $x&gt;0$. Prove that $g$ is monotonically increasing.  Source: W. Rudin, Principles of Mathematical Analysis, Chapter 5, exercise 6. What is the difference between 'sudo' and 'su -c' Normed vector spaces over finite fields Normed vector spaces are typically defined over the reals or complex numbers.  Is there any "standard," well-behaved construction that generalizes this to a vector space over a finite field, such as $\Bbb F_2$?  I'm looking for something kind of like the class of $\ell_p$ norms, except designed with finite fields in mind.  Ideally, something that has deep fundamental properties making it well-behaved in the same way that the Euclidean norm is. Where do I ask where to ask? If I have a specific question I want to ask about, but I don't know which Stack Exchange site would be on topic for asking that question, where can I ask where to ask that question?  Is there any generic place where we can ask for advice? Is it here?  This is not about a specific question but in general.  For example: "Where should I ask for advice about fishing?", or if I need to know where I should ask "What would be the best fishing rod to fish for salmon?" (regardless of how good/bad these examples are) I would like to have a similar biblatex behaviour as described , i.e. separate bibliographies for different publication types, each bibliography should 1) be prefixed with a corresponding label (C for conference publications, J for journals etc), 2) sorted so that the newest entry is at the top (defined by the publication year) and 3) with reference numbers sorted in descending order per bibliography, i.e. the newest entry should have the highest number.  Journal articles ---------------- [J3]    reference from 2017 [J2]    reference from 2016 [J1]    reference from 2015  Conference publications ----------------------- [C4]    reference from 2017 [C3]    reference from 2017 [C2]    reference from 2016 [C1]    reference from 2015   I currently have the following:  \usepackage[backend=biber,         isbn=true,         giveninits=true,         style=numeric,         maxnames=99,         sorting=ydnt,         defernumbers=true,         autocite=superscript]{biblatex}  \subsection*{Journal articles} \begin{refcontext}[labelprefix=J] \printbibliography[type=article] \end{refcontext}  \subsection*{Conference publications} \begin{refcontext}[labelprefix=C] \printbibliography[type=inproceedings]   Separate bibliographies works fine, labelprefix also works as desired, sorting by year in descending order as well. However, if I try the solution mentioned in the above question I get very high reference numbers (in the 500s).  Is the above behaviour possible at all and, if yes, what is the most elegant solution using current biblatex etc.?  Thanks a lot in advance! table side by side with minipage I can't manage to get two tables side by side in a minipage environment. Any kind suggestion would be highly appreciated!   \documentclass{article} \usepackage{array}  \begin{document} \begin{table}[htbp] \centering \begin{minipage}{.2\textwidth}     \begin{tabular}{| m{3cm} | m{4.3cm} | c |}   \hline  number of entity filter (size 1) &amp; number of context filters (size 2, size 3,  size 4) &amp; Accuracy\\ [2ex]   \hline  32  &amp;  32  ,  32  ,  32  &amp;  0.835 \\[0.5ex] \hline 32  &amp;  64  ,  64  ,  64  &amp;  0.821 \\[0.5ex] \hline 32  &amp;  128  ,  128  ,  128  &amp;  0.819 \\[0.5ex] \hline 32  &amp;  256  ,  256  ,  256  &amp;  0.749 \\[0.5ex] \hline 32  &amp;  512  ,  512  ,  512  &amp;  0.683 \\[0.5ex] \hline 32  &amp;  1024  ,  1024  ,  1024  &amp;  0.528 \\[0.5ex] \hline 32  &amp;  2048  ,  2048  ,  2048  &amp;  0.235 \\[0.5ex] \hline 64  &amp;  32  ,  32  ,  32  &amp;  0.850 \\[0.5ex] \hline 64  &amp;  64  ,  64  ,  64  &amp;  0.816 \\[0.5ex] \hline 64  &amp;  128  ,  128  ,  128  &amp;  0.786 \\[0.5ex] \hline 64  &amp;  256  ,  256  ,  256  &amp;  0.795 \\[0.5ex] \hline 64  &amp;  512  ,  512  ,  512  &amp;  0.765 \\[0.5ex] \hline 64  &amp;  1024  ,  1024  ,  1024  &amp;  0.669 \\[0.5ex] \hline 64  &amp;  2048  ,  2048  ,  2048  &amp;  0.331 \\[0.5ex] \hline 128  &amp;  32  ,  32  ,  32  &amp;  0.920 \\[0.5ex] \hline 128  &amp;  64  ,  64  ,  64  &amp;  0.890 \\[0.5ex] \hline 128  &amp;  128  ,  128  ,  128  &amp;  0.886 \\[0.5ex] \hline 128  &amp;  256  ,  256  ,  256  &amp;  0.846 \\[0.5ex] \hline 128  &amp;  512  ,  512  ,  512  &amp;  0.789 \\[0.5ex] \hline 128  &amp;  1024  ,  1024  ,  1024  &amp;  0.755 \\[0.5ex] \hline 128  &amp;  2048  ,  2048  ,  2048  &amp;  0.488 \\[0.5ex] \hline 256  &amp;  32  ,  32  ,  32  &amp;  0.920 \\[0.5ex] \hline 256  &amp;  64  ,  64  ,  64  &amp;  0.922 \\[0.5ex] \hline 256  &amp;  128  ,  128  ,  128  &amp;  0.912 \\[0.5ex] \hline 256  &amp;  256  ,  256  ,  256  &amp;  0.877 \\[0.5ex] \hline 256  &amp;  512  ,  512  ,  512  &amp;  0.872 \\[0.5ex] \hline 256  &amp;  1024  ,  1024  ,  1024  &amp;  0.771 \\[0.5ex] \hline 256  &amp;  2048  ,  2048  ,  2048  &amp;  0.683 \\[0.5ex]  \hline  \end{tabular} \end{minipage}% \hfill \begin{minipage}{.2\textwidth}     \begin{tabular}{| m{3cm} | m{4.3cm} | c |}   \hline  number of entity filter (size 1) &amp; number of context filters (size 2, size 3,  size4) &amp; Accuracy\\ [2ex]   \hline 512  &amp;  32  ,  32  ,  32  &amp;  0.910 \\[0.5ex] \hline 512  &amp;  64  ,  64  ,  64  &amp;  0.922 \\[0.5ex] \hline 512  &amp;  128  ,  128  ,  128  &amp;  0.909 \\[0.5ex] \hline 512  &amp;  256  ,  256  ,  256  &amp;  0.910 \\[0.5ex] \hline 512  &amp;  512  ,  512  ,  512  &amp;  0.883 \\[0.5ex] \hline 512  &amp;  1024  ,  1024  ,  1024  &amp;  0.730 \\[0.5ex] \hline 512  &amp;  2048  ,  2048  ,  2048  &amp;  0.682 \\[0.5ex] \hline 1024  &amp;  32  ,  32  ,  32  &amp;  0.925 \\[0.5ex] \hline 1024  &amp;  64  ,  64  ,  64  &amp;  0.931 \\[0.5ex] \hline 1024  &amp;  128  ,  128  ,  128  &amp;  0.920 \\[0.5ex] \hline 1024  &amp;  256  ,  256  ,  256  &amp;  0.917 \\[0.5ex] \hline 1024  &amp;  512  ,  512  ,  512  &amp;  0.899 \\[0.5ex] \hline 1024  &amp;  1024  ,  1024  ,  1024  &amp;  0.858 \\[0.5ex] \hline 1024  &amp;  2048  ,  2048  ,  2048  &amp;  0.776 \\[0.5ex] \hline 2048  &amp;  32  ,  32  ,  32  &amp;  0.933 \\[0.5ex] \hline 2048  &amp;  64  ,  64  ,  64  &amp;  0.934 \\[0.5ex] \hline 2048  &amp;  128  ,  128  ,  128  &amp;  0.925 \\[0.5ex] \hline 2048  &amp;  256  ,  256  ,  256  &amp;  0.928 \\[0.5ex] \hline 2048  &amp;  512  ,  512  ,  512  &amp;  0.907 \\[0.5ex] \hline 2048  &amp;  1024  ,  1024  ,  1024  &amp;  0.878 \\[0.5ex] \hline 2048  &amp;  2048  ,  2048  ,  2048  &amp;  0.798 \\[0.5ex]  \hline  \hline \end{tabular} \end{minipage} \caption{filter window size} \label{tab:config_filternum} \end{table}   \end{document}   What I have so far  EDIT: I followed the second solution from , and it somehow didn't work. I am not sure why. How much electronics and other valuables can I bring duty-free when going to India? I'm a bachelor student majoring in math, and pretty interested in physics. I would like a book to study for classical mechanics, that will prepare me to work through . What books would be good for a beginner? What does "+6 to hit, Hit: 13 (2d8 + 4)" mean in a creature's stat block? My friends and I are very new to D&amp;D, played like 3 times. In a monster's stats next to weapon damage it says stuff like "+11 to hit" and "Hit: 5 (1d8+1)". For the premade characters it just says things like "+4, 2d6 + 2 slashing", though. Why are there two "hit" numbers for monsters? Which do I use for the d20 roll to hit against a target's AC?  I mean for example like in the Ogre entry in the "" article on monsters. Suppose that $\hat{x}$ is the least squares solution of $Ax = b$.  That is, $\min{|r|}, r = Ax - b$ with respect to $x$.  Is $\hat{x}$ also the least squares solution of $JAx = Jb$?  I suspect so, but I'm not sure how to prove it.  If $J$ is invertible, it's easy enough to prove as you can just cancel it out from both sides.  But what if it's not invertible? Pass C# ASP.NET array to Javascript array If $A^2 = I$, then $\operatorname{rank} (A+I) + \operatorname{rank} (A-I) =n$ If $A^2 = I$ where $A$ is an $n\times n$ matrix, then why is $\operatorname{rank} (A+I) + \operatorname{rank} (A-I) =n$.   I am not sure why this seems to be true. I just saw Death in Paradise Season 5 Episode 3, which features a photographer using a DSLR to shoot a fashion runway performance.  He had a flash that was a ring around the lens.   I thought that was for macro shots only, where the extreme close-up has trouble with normal flash placement.  For normal photos you want the flash far from the lens, like on a boom on a separate handle framing the camera.  I've seen some recent trendiness in having ring-shaped catch lights, but I supposed those would be positioned in the normal manner: off-angle from the lens.  I suppose if an on-camera had any effect at all it would be for some subtle fill flash.  Is this a realistic thing to see from a pro? Or is it just a cool-looking prop that doesn't really fit the situation? One of whom destroys the Earth, perhaps accidentally, while fighting another... the plot also involves a human colony ship or planet that loses contact with the Earth; I think a small boy is also involved with the plot, although it's been 20-30 years since I read this story.  Any help would be appreciated!  It's driving my brother and me a bit batty.  Here's the batty brother's take: the main being has created others who are now at war, exploding stars. To escape, the main being accelerates the star of the human colony as a decoy. However, most of the story centers on some guy who winds up living forever, as they keep sticking him in cryogenic sleep and reawakening him. If memory serves me right, they abandon the colony planet for a while and move to asteroids as the star is weakening because it is using it's energy to accelerate. When it decelerates, it is the only star left in the universe. The one "being" was almost reduced to living off the energy of a black hole when it appears, and he sees it and sets off to go there, with a cryptic ending that the humans very well might fight him off. To show that Fermat number $F_{5}$ is divisible by $641$. How can I show that  $F_{5}=2^{2^5}+1$ is divisible by $641$. Converting string of 1s and 0s into binary value I'm trying to convert an incoming sting of 1s and 0s from stdin into their respective binary values (where a string such as "11110111" would be converted to 0xF7). This seems pretty trivial but I don't want to reinvent the wheel so I'm wondering if there's anything in the C/C++ standard libs that can already perform such an operation?