I have added a "boxed x" and "CHECK MARK" to my document, but they do 
not get exported to pdf output.  They are in the .tex file, and do go 
through to the HTML.  So far I'm using these packages

    #+LaTeX_HEADER: \usepackage[T1]{fontenc}
    #+LaTeX_HEADER: \usepackage{libertine}
    #+LaTeX_HEADER: \usepackage[margin=0.80in]{geometry}
    #+LaTeX_HEADER: \usepackage{setspace}
    #+LaTeX_HEADER: \usepackage{enumitem}
    #+LaTeX_HEADER: \usepackage{endnotes}

(Bonus points for UTF8 code for the opposite of "CHECK MARK"?)