I am having problems going to a HP Laserjet 5Si MX network printer.  It
   acts like an ordinary lpd type printer except it won't add a CR to newline
   so I am trying to add a filter to add them in.  Problem is that lpd won't
   run a filter for remote printers.  Since I can't muck around on the HP,
   can someone suggest the magic I need to add the CR in?

Although fixing lpd (as suggested by someone else or by using LPRng
which allows sending output directly to the printer via a special
port) is perhaps the best approach, a quick work-around involves
creating two queues.  One queue does filtering and resubmits the job
to the second queue which passes it to the remote printer.  Set up
your printcap like (which works fine with HPs print server boxes):

ljet6mp|HP LaserJet 6MP:\
	:if=/usr/libexec/lpr/ljet6mp-filter:\
	:lf=/var/log/lpd-errs:\
	:lp=/dev/null:\
	:mx#0:\
	:sd=/var/spool/lpd/ljet6mp/default:\
	:sh:
ljet6mp-raw|HP LaserJet 6MP:\
	:lf=/var/log/lpd-errs:\
	:mx#0:\
	:rm=printserver:\
	:rp=raw:\
	:sd=/var/spool/lpd/ljet6mp/raw:

and have your filter do whatever needs to happen along with piping its
output to lpr -P...

Cheers,
Brook