When in the past I have knitted an .Rmd file, it has automatically displayed the final pdf file using pdfLaTeX. Suddenly the display of the pdf file is no longer happening automatically. It's easy enough to display the file manually using Acrobat Reader, but one nice thing about pdfLaTeX is that it permits overwriting and reopening the viewer when I reknit the file. With Acrobat Reader I have to remember to close the pdf before reknitting.
Is there an easy way for me to reset the system to use pdfLaTeX to open the pdf files automatically following knitting an Rmd file?
I know you can change how (or if) you see the preview in Tools > Global Options > R Markdown > Show output preview in. I think the default is "Window", but it can be set to "(None)" so you might check if that is the case for you.
Thanks, aosmith! That turns out to be exactly what happened. I'm pretty sure that I didn't change the option. (I rarely go to the Options tabs.) But the option to display a preview had certainly become unchecked. Rechecking it fixed the problem.