devtools::check() with qpdf

#' Eureka!
#' 
#' Running `devtools::check()` on my Windows laptop,
#' I kept getting the following warning:
#' 
#' ```
#' 'qpdf' is needed for checks on size reduction of PDFs
#' ```
#' 
#' I downloaded the latest version of `qpdf` from SourceForge,
#' but I don't have admin rights to add it to my Windows PATH.
#' So instead I ran the following:
devtools::check(
  env_vars = list(
    PATH = paste(
      Sys.getenv("PATH"),
      "C:\\Users\\wolfebe1\\Software\\qpdf\\bin",
      sep = ";"
    )
  )
)

#' Bam! Zero warnings!