This helper function converts a vector of images to a single PDF.
image_to_pdf(files, pdf_name)
no return value, called for side effects
Combines any number of image files of almost any type to a single PDF. The vector can consist of different image file types. See the 'Magick' package documentation https://cran.r-project.org/package=magick for details on supported file types. Note that on Linux, ImageMagick may not allow conversion to pdf for security reasons.