download.R

urls <- c(
  "http://www.unicef.org/spanish/sowc06/pdfs/sowc06_fullreport_sp.pdf",
  "http://www.unicef.org/spanish/sowc2012/pdfs/SOWC-2012-Main-Report-LoRes-PDF_SP_01052012.pdf",
  "http://www.unicef.org/honduras/estado_mundial_de_la_infancia_conemoracion_20_anos.pdf"
)

for (url in urls) {
  newName <- paste (format(Sys.time(), "%Y%m%d%H%M"), "-", basename(url), sep =" ")
  download.file(url, destfile = newName)
}