Following example.org is expected to be exported in landscape though the generated pdf remains in portrait. What should I change?
** A3 PDF Landscape
#+LATEX_HEADER: \usepackage[a3paper]{geometry}
#+LATEX_HEADER: \usepackage[lscape]{geometry}
#+ATTR_LATEX: :placement [H] :landscape
*** Flowchart landscape
#+BEGIN_SRC mermaid :file myPicture1121.png
graph LR
john-->|calls|mary
#+END_SRC
#+RESULTS:
[[file:myPicture1121.png]]

#+LATEX_CLASS_OPTIONS: [landscape]you linked. Not sure why thegeometrypackage doesn't work for you, though. – Lorenz Aug 08 '19 at 08:12