Are there any rules for making your own NPCs, or guidelines for balancing encounters? I couldn't seem to find them.

There are not any rules about encounters and NPCs.

The Link is to the Dark Heresy forums to a similar question about encounters.

NPCs, depending on who or what they are likely need little more than a stat line and a number of wounds. Most NPCs can get by with nothing more than a base 25 stat for everything with higher ups getting a +5 or +10 to 2-3 stats. I will only stat out and give specific talents, skills, equipment to very special, major characters and even those are not full character work ups.

Thanks man. I guess there's so many ways to deal with a problem in this game it doesn't really need to be balanced in the conventional sense.