Today I had a “pandoc document conversion failed with error 43” error when compiling a document in Rstudio and directly with rmarkdown. Such an error used to occur a couple of years ago, but that bug has long been fixed. At first I was a bit puzzled, given that this was a rather simple document. It turned out that this error can be a sign of a poorly specified ‘date’ argument in the header, more specifically pandoc does not like a period there.
So
---
title: "Something"
author: "Didier Ruedin"
date: "7 March 2017"
output: pdf_document
---
works, while
---
title: "Something"
author: "Didier Ruedin"
date: "7. March 2017"
output: pdf_document
---
does not. In German, typically there is a period in dates, like 7. März 2017.
Didier Ruedin 
It can also be a mistake from creating formulas in LaTeX. Misplacing something like \( \bar{x} with one space too much between the equation triggered the error for me.
Thanks, that’s good to know!
I had a similar problem with a “leading” period in title argument, like so:
title: “1. Title”
Removing the period solved the problem. Also, a period after the letters does not cause a problem, like so:
title: “Title.”
Thanks, that’s good to know what exactly works and what doesn’t!