Insert a blank page on every page break?

Question

I have slides (slides.pdf; my own construction based on scrartcl) to teach from. Students asked to put in blank slides (to have space to put down notes). I first tried to write a shell script (getting the page number from slides.pdf, creating a second document blanks.pdf (same number of pages) with just blank pages, then merging the two with pdftk), but it's tedious and requires various tools. I am wondering if this can be done in LaTeX. I only have some explicit \clearpage statements, but when there are longer formulas (extending over a page), there is an automatic page break on the slides. I could imagine LaTeX knows when these page breaks happen, so if there is a way to tell LaTeX to put in two page breaks instead of just one, that would nicely give empty pages. Any ideas? Ideally, the page numbers should not advance... hope that's possible (?)

\documentclass{scrartcl}
\usepackage{amsmath}
\usepackage{bm}
\usepackage{blindtext}
\begin{document}
\blindtext[4]
{\allowdisplaybreaks
  \begin{align*}
    &\phantom{{}\Leftrightarrow{}}\ \langle X_n-\hat{X}_n,Y\rangle=0,\quad\forall\,Y\in\mathcal{H}_{n-1}\\
    &\Leftrightarrow\ \underbrace{\langle
      X_n-\hat{X}_n,\sum_{k=1}^{n-1}\alpha_kX_{n-k}\rangle}_{=\,\sum_{k=1}^{n-1}\alpha_k\langle
      X_n-\hat{X}_n,X_{n-k}\rangle}=0,\quad\forall\,\alpha_1,\dots,\alpha_{n-1}\\
    &\Leftrightarrow\underbrace{\langle X_n-\hat{X}_n,X_l\rangle}_{\substack{
      =\,E((X_n-\sum_{k=1}^{n-1}\phi_{n-1,k}X_{n-k})X_l)\\
    =\,E(X_nX_l)-\sum_{k=1}^{n-1}\phi_{n-1,k}E(X_{n-k}X_l)}}\hspace{-10mm}=0,\quad\forall\,l\in\{1,\dots,n-1\}\\
    &\Leftrightarrow\ \gamma(n-l)=\sum_{k=1}^{n-1}\gamma(n-k-l)\phi_{n-1,k}\\[-1mm]
    &\Leftrightarrow\ \gamma(h)=\sum_{k=1}^{n-1}\gamma(h-k)\phi_{n-1,k},\quad\forall\,h\in\{1,\dots,n-1\}\\[-1mm]
    &\Leftrightarrow\
      \Gamma_{n-1}\bm{\phi}_{n-1}=\bm{\gamma}_{n-1}
  \end{align*}}%
\end{document}

I also found this and then tried the solution there, but it only puts in one empty page (on the next page break after the command). I wonder if this can be adjusted (?)

Another option would be to actually use a two-sided layout (and put in empty pages if the page is an even page)... but that seems to be quite a bit intrusive.

Longer Update

A minimal example of what John suggested worked well. However, when I put it in my real document, I obtained weird errors. I then did the obvious, namely minimize the document to a MWE. Here it is. And, yes, it is minimal... whenever I omit a line of the following, it will produce an error, even if I replace words in the text by other words... very strange. The error is:

LaTeX Error: Something's wrong--perhaps a missing \item.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.58   \item A
               (model for)
? 

\documentclass[paper=128mm:96mm, parskip=half-]{scrartcl}
\linespread{1.12}
\usepackage[T1]{fontenc}
\usepackage[american]{babel}
\usepackage{microtype}
\usepackage[includefoot, left=5mm, right=5mm, bottom=3.5mm, top=4mm, footskip=4mm]{geometry}
\usepackage{titlesec}
\usepackage{enumitem}
\usepackage{biblatex}
\usepackage{filecontents}
\usepackage{afterpage}
\setlist{
  align=left,
  labelsep=*,
  leftmargin=*,
  topsep=-1.2mm,
  itemsep=-1.4mm
}
\titlespacing{\subsubsection}{0mm}{0ex plus 1ex minus .2ex}{-0.8ex plus .2ex}
\setcounter{secnumdepth}{3}
\newcommand{\insertblanks}{\strut\newpage\afterpage{\insertblanks}}
\begin{filecontents*}{bib.bib}
@ARTICLE{bib:markowitz-52,}
@ARTICLE{bib:harrison-kreps-79,}
@ARTICLE{bib:harrison-pliska-81,}
\end{filecontents*}
\begin{document}
\afterpage{\insertblanks}
\subsection{Foo}
\subsubsection{Bar}
\subsubsection*{Foobar}
\begin{itemize}
\item foo bar foo bar
  \begin{itemize}
  \item or sell (\emph{put}) an asset at an agreed-upon
price (the \emph{strike price $K$}) during a predetermined period
(\emph{American}) or date (\emph{exercise date $T$}; \emph{European});
  \item \emph{Futures} (obligation for the buyer (seller) to purchase (sell) an asset at a predetermined date and price);
  \item \emph{Swaps} (any exchange of an asset for another to change the
         maturity (e.g., of a bond) or because investment objectives have changed; include currency swaps, interest rate swaps).
  \end{itemize}
\item Babylon of 1800 BC: early evidence for options to provide financial cover against crop failure
\end{itemize}
\subsubsection*{Academic innovation in the 20th century}
\begin{itemize}
\item Before 1950: Desirability of an investment was measured in terms of
its return.
\item \textcite{bib:markowitz-52}: Desirability of an investment was decided upon a risk-return diagram
(x-axis: risk, i.e., standard deviation; y-axis: expected
return). An \emph{efficient frontier} determined the optimal return for a
\item Late 20th century: Theory
      milestone for quantifying and managing financial risk)
\item Black--Scholes--Merton formula
      for the price of a European call option (Nobel Prize 1997)
\item \textcite{bib:harrison-kreps-79}, \textcite{bib:harrison-pliska-81}:
  Fundamental theorems of asset pricing
  \begin{enumerate}
  \item A (model for)
  \end{enumerate}
\end{itemize}
\end{document}

Answer 1

Note: \newpage, \pagebreak and \clearpage do nothing to an empty page, so you need to add something invisible first. BTW, \clearpage is used primarily to clear the float queue.

\documentclass{scrartcl}
\usepackage{amsmath}
\usepackage{bm}
\usepackage{afterpage}
\usepackage{mwe}

\newcommand{\repeatafter}{%
  \thispagestyle{empty}%
  \addtocounter{page}{-1}%
  \null\newpage
  \afterpage{\repeatafter}%
}

\begin{document}
\afterpage{\repeatafter}

\lipsum[1-16]
\end{document}

Answer 2

Take a look at the package afterpage, which seems to do exactly what you would want. Load it in the preamble, and then on every page put \afterpage{${}$\clearpage}. It seems just \afterpage{\clearpage} doesn't do the job, so I put in an empty symbol ${}$ to make it work.

There's probably a neater way of doing this with this package, but that's the direction you should go.

Answer 3

Due to my problems with the MWE I posted I realized another solution: I use geometry and scrartcl's paper option for creating slides in the right format. A very simple but powerful solution is then to simply adjust the bottom argument of geometry paired with a larger paper height. This way one 'fakes' a larger page and gets white space below each slide.

Answer 4

My suggestion (as your first attempted shell script), would be to make a new file, which takes your slides.pdf and gives a new pdf that includes the empty pages. The package pdfpages is very powerful for these kind of things. For your purpose, you can do the following:

\documentclass{article}
\usepackage{pdfpages}
\begin{document}

\includepdf[pages=-, fitpaper=true, pagecommand={\null\newpage}]{slides.pdf}

\end{document}

The pages=- option makes it take all the pages of the given pdf. The fitpaper=true makes the pages of the new pdf exactly the same size as your first original page. The pagecommand={\null\newpage} adds a new page after each inserted page. (The \null here is to put something empty on a new page).

Downside: this removes features of the document (as it just prints the pdf pages in a new pdf), like reference links in the file or the table of content in the pdf viewer. If this file is intended for printing, this does not matter.