Guide to build PDF for non-ASCII language

docs/guides/pdf-non-ascii-languages.rst

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+Build PDF format for non-ASCII languages
+========================================
+
+
+.. warning::
+
+   To be able to follow this guide and build PDF with this method,
+   you need to ask to enable ``USE_PDF_LATEXMK`` :doc:`feature flag </guides/feature-flags>` in your project.
+   Please, `open an issue`_ in our repository asking for this and wait for one of the core team to enable it.
+
+.. _open an issue: https://github.com/rtfd/readthedocs.org/issues/new
+
+
+Sphinx comes with support for different `LaTeX engines`_ that support non-ASCII languages,
+like Japanese or Chinese, for example.
+By default Sphinx uses ``pdflatex``,
+which does not have good support for Unicode characters and may make the PDF builder to fail on these languages.
+
+.. _LaTeX engines: http://www.sphinx-doc.org/en/master/usage/configuration.html#confval-latex_engine
+
+In case you want to build your documentation in PDF format you need to configure Sphinx properly,
+so Read the Docs can execute the proper commands depending on these settings.
+There are `several settings that can be defined`_ (all the ones starting with ``latex_``),
+to modify Sphinx and Read the Docs behavior to make your documentation to build properly.
+
+A good first try would be to use only ``latex_engine = 'xelatex'`` in your ``conf.py``,
+if your docs are not written in Chinese or Japanese.
+This is because your build could be failing just because of an Unicode error
+(which ``xelatex`` has better support for them than the default ``pdflatex``)
+
+.. _several settings that can be defined: http://www.sphinx-doc.org/en/master/usage/configuration.html#options-for-latex-output
+
+When Read the Docs detects that your documentation is in Chinese or Japanese it automatically adds some defaults for you.
+
+For *Chinese* projects, it appends to your ``conf.py`` these configurations:
+
+.. code-block:: python
+
+    latex_engine = 'xelatex'
+    latex_use_xindy = False
+    latex_elements = {
+        'preamble': '\\usepackage[UTF8]{ctex}\n',
+    }
+
+And for *Japanese* projects:
+
+.. code-block:: python
+
+    latex_engine = 'platex'
+    latex_use_xindy = False
+
+.. tip::
+
+   You can always override these configurations if you define them by yourself in your ``conf.py`` file.
+
+.. note::
+
+   ``xindy`` is currently not supported by Read the Docs,
+   but we plan to support it in the near future.