lpr is part of the BSD-style print queue system, which is being phased out
over the next few years in favor of the System-V-style system.  As of
HP-UX 10.00, the SYSV system is bundled.  Here's a quick cheatsheet:

    lpr -Pvaxps         -> lp -dvaxps
    lpq -Pvaxps         -> lpstat vaxps
    lprm -Pvaxps ID     -> cancel vaxps ID

Why would I want to switch over to the System-V-style HP-UX LP spooler?

Because you can do neat things like:

  $ lp -dvaxps -odouble FILENAME

which will print double-sided, that is, on both sides of the paper, if
your printer supports it.

How do I send output from nroff to HP LaserJet printers?

Try this:

  $ nroff -Tlj ... | lp -onroff