Entering unicode character for Chi-Rho in LaTeX

Question

I am in the middle of a very long document (which means I will not be able to switch to XeTeX or LuaTeX), and everything is close to done with the exception of a few missing symbols. The symbols all exist as unicode characters; for now, I'm working on the Chi Rho symbol. It exists as a unicode symbol, but it does not exist in the Comprehensive LaTeX Symbol List. Does that mean that I cannot insert this character into my document in some way (other than trying to draw something)?

Answer 1

You can compile the ☧ symbol as a standalone PDF, with LuaLaTeX or XeLaTeX, and include it. This embeds the Unicode font you used into your PDFTeX document. You can even copy and paste it.

First, compile this to chiro.pdf with LuaLaTeX or XeLaTeX: Upload it with your project as a graphic.

\documentclass{standalone}
\tracinglostchars=2
\usepackage{libertinus}
\begin{document}
☧
\end{document}

You can then embed the document in PDFLaTeX. This code with automatically scale the symbol to the height of a capital letter in the current font.

\documentclass{article}
\tracinglostchars=2
\usepackage{libertinus}
\usepackage{graphicx} % For \includegraphics
\usepackage{parskip}
\newlength{\capheight}
\newcommand\ChiRo{%
  \settoheight{\capheight}{P}%
  \includegraphics[height=\capheight]{chiro.pdf}}
\begin{document}
Chi-Ro: {\ChiRo}.
{\Huge A big \ChiRo}
{\footnotesize A small \ChiRo}
\end{document}

If you want to use the Unicode character ☧ in your source, you can add the lines

 \usepackage{newunicodechar}
 \newunicodechar{☧}{\ChiRo}