pandoc document conversion failed with error 41

Solution:
Step 1: Download and Install MiKTeX from http://miktex.org/2.9/setup
Step 2: Run Sys.getenv("PATH") in R studio 
This command returns the path where Rstudio is trying to find pdflatex.exe
In windows (64-bit) it should return C:\Program Files\MiKTeX 2.9\miktex\bin\x64\pdflatex.exe

If pdflatex.exe is not located in this location Rstudio gives this error code 41.
Step 3: To set this path variable run:
Sys.setenv(PATH=paste(Sys.getenv("PATH"),"C:/Program Files/MiKTeX 2.9/miktex/bin/x64/",sep=";"))

https://github.com/rstudio/shiny-examples/issues/34