\newgeometry ignores the landscape option so you won't be able to switch from portrait to landscape orientation in the middle of your document. You can use the landscape environment from the pdflscape package, but this won't take care of headers/footers or page numbers:
\documentclass[leavefloats]{apa6e}
\usepackage{,pdflscape}
\usepackage{lipsum}
\abstract{This is an example of of an abstract in APA. }
\title{A Template for APA Papers}
\shorttitle{APA: A Template}
\author{John}
\authornote{\dots}
\date{\today}
\begin{document}
\maketitle
\lipsum[1-10]
\begin{landscape}
\lipsum[1-10]
\end{landscape}
\end{document}
The landscape environment doen't rotate the header; to keep the header as defined in apa6e.cls when in landscape orientation, you could first remove the header/footer using \pagestyle{empty} and then use the background package to place the header; something along these lines:
\documentclass[leavefloats]{apa6e}
\usepackage[american]{babel}
\usepackage{pdflscape}
\usepackage{background}
\usepackage{lipsum}
\SetBgScale{1}
\SetBgColor{black}
\SetBgOpacity{1}
\SetBgAngle{90}
\SetBgPosition{current page.west}
\SetBgVshift{-1.3cm}
\SetBgContents{}
\abstract{This is an example of of an abstract in APA. }
\title{A Template for APA Papers}
\shorttitle{APA: A Template}
\author{John}
\authornote{\dots}
\date{\today}
\makeatletter
\let\StShortTitle\@shorttitle
\makeatother
\begin{document}
\maketitle
\section{lkadfjsjkdfg}
\subsection{test}
\lipsum[1-10]
\begin{landscape}
\pagestyle{empty}
\SetBgContents{%
\begin{minipage}[c][1.2\textwidth][c]{22.8cm}
\noindent\MakeUppercase{\StShortTitle}\hfill\thepage
\end{minipage}%
}
\lipsum[1-10]
\end{landscape}
\end{document}
Once you get the error message:
! LaTeX Error: Option clash for package xcolor.
See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help.
...
l.17
type "h" (without the quotation marks, for help) in the output console and you get
? h
The package xcolor has already been loaded with options:
[]
There has now been an attempt to load it with options
[table]
Adding the global options:
,table
to your \documentclass declaration may fix this.
So, you get an explanation of the problem and a possible solution. Doing as advised you prevent the clash:
\documentclass[a4paper,oneside,article,table]{memoir}
\usepackage[latin1]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[danish]{babel}
\usepackage{lmodern}
\usepackage{graphicx}
\graphicspath{{Figures/}}
\usepackage{fullpage}
\usepackage{modroman}
\usepackage{float}
\usepackage{caption}
\usepackage[numbers]{natbib}
\usepackage{url}
\usepackage{pgfplots}
\usepackage{mathtools}
\usepackage{xcolor}
\begin{document}
test
\end{document}
Now, the problem was that another package (pgfplots, in this case) had already loaded the xcolor package without options, so loading it after pgfplots with the table option produces the clash. One way to prevent the problem was already presented (using table as class option); another solution is to load xcolor with the table option before pgfplots:
\documentclass[a4paper,oneside,article]{memoir}
\usepackage[latin1]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[danish]{babel}
\usepackage{lmodern}
\usepackage{graphicx}
\graphicspath{{Figures/}}
\usepackage{fullpage}
\usepackage{modroman}
\usepackage{float}
\usepackage{caption}
\usepackage[numbers]{natbib}
\usepackage{url}
\usepackage[table]{xcolor}
\usepackage{pgfplots}
\usepackage{mathtools}
\begin{document}
test
\end{document}
Best Answer
Apparently the class
vldbis already loadinggeometrywith settings different from what you'd like to get.If the class is for submissions to a journal or a conference, don't set new values for
geometry. Otherwise simply dowhere you have
\usepackage[...]{geometry}. The new values will override those set by the class.