I do not know any LaTeX libraries and, as you said, this does not seem trivial, so I am also a bit strange. I always wrote documents myself using the TeXnic Center IDE tags, which I found very useful.
You can always try to write the document source to a file using StreamWriter, and then start a new pdflatex process through the command line in the code to compile the document in pdf?
Also, I managed to stumble upon a list of open source PDF generation libraries for C # that might be worth a look here (I don't think they are, unfortunately, for LaTeX for them):
http://en.csharp-online.net/Open_Source_PDF_Libraries
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