I'm using knitr to convert .Rnw files to .pdf files. I can use Skim to jump from a position in the .pdf file to the .tex file produced by knitr.
How can I jump from a position in the .pdf file to the .Rnw?
Check out SyncTeX. For example, RStudio's PDF viewer provides a synchronization between the PDF and the underlying Rnw file, see here or here.