If you need to convert a lot of pages in a batch, and you feel that wkhtmltopdf is a bit too slow to start up, then you should try --read-args-from-stdin, When --read-args-from-stdin each line of input sent to wkhtmltopdf on stdin will act as a separate invocation of wkhtmltopdf, with the arguments specified on the given line combined with the arguments given to wkhtmltopdf