Greetings,
I'm new to pathfinder myself, but I'll throw out a few suggestions that come to mind here.
One easy option would seem to be up the CR level for each encounter. I don't have enough experience to say how much other than what is said in the core rulebook.
You have 6 players of level one, so your Average Party Level (APL) is 1 then you add one +1 because your group consists of six or more players. So your APL is now 2.
So now an average encounter would now have a CR 2 for a six player group. A challenging encounter would now be 3, and so on.
Since I'm new as well, so I can only tell you how I would do it.
I'd personally go for a CR of 3 on the first encounter, see how it goes. Because
That way, you can see how the CR affects the group right off the bat, and maybe have preplanned CR2 and CR3 encounters for the remaining ones.
If it's too easy, backup can always arrive :)
For a new pre-gen, I think rolling up another fighter or barbarian would be the easiest time wise. I'd just give them slightly different equipment and feats so they feel different, and so that they better complement a six player group.
Otherwise you'll have to dig through the PRD or core rulebook. http://paizo.com/pathfinderRPG/prd/
Thanks for your post. You made me think about this as well. Don't know if any of that helps.
Cheers!
