A lot of people are interested in playing low-magic campaigns. Unfortunately, this doesn't really work in any variation of 3e, including Pathfinder. There are thus two options to make low-magic function in your home game.
1. Play E6. Stop the game around level six.
2. Listen to me. You mad?
Let's start off with the basics about Pathfinder. At a certain point, you need magical equipment to overcome damage reduction. If you're playing in a game and you encounter DR 15/magic and you don't have a magic sword, you're screwed (unless you have a wizard nearby who can kill the monster for you...which would be using magic). You are also going to be fighting explicitly magical creatures who can cast spells and have access to a host of supernatural abilities. While you might be playing in a low-magic game, the dragons, demons, and fey that you will encounter are not. Because it is assumed that you have a certain amount of magical equipment at each levels, monsters are designed according to such. Unless the DM plans on throwing low CR monsters against you and eyeballing how tough they are compared to your magicless stats, you're in for an extremely rough ride.
Instead of that particular mess, I'm going to present a system for you that allows you to have all the mystery and wonder of a low-magic setting without the headache of pathetic characters. As your characters level up, instead of gaining magic items, they gain inherent bonuses to their abilities. For some people, this will defeat the purpose of a low-magic game. These people should take suggestion #1 and play E6. For others, this may solve the dilemma of having to hand out magic items like candy.
Now, before I introduce the level-by-level guide itself, you need to know that I'm not going to bother with the minutiae that typically suffuses a Pathfinder game. Bonus types, stacking, and so forth don't matter. If you're playing a low-magic game, you're not getting magic items, and you don't have a wizard to throw buffs on everyone. No druids are turning themselves into bears, no clerics are casting righteous might. If they are, you're probably not actually playing a low-magic game. You're playing a "screw the non-casters" game, where the spellcasters get all their nice abilities but the disenfranchised fighter is swining a +1 sword at level 17. But even if that's your style, assume that none of these bonuses stack with any other like bonus. In addition, the later bonuses supercede those from previous levels.
Level 3: You gain a +1 bonus on attack and damage rolls. You gain a +1 bonus to your Armor Class. All your attacks are treated as magical for the purposes of overcoming damage reduction.
Level 4: You gain a +2 bonus to a single ability score of your choosing. You gain a +1 bonus on attack and damage rolls. You gain a +1 bonus to your Armor Class. All your attacks are treated as magical for the purposes of overcoming damage reduction.
Level 5: You gain a +2 bonus to two ability scores of your choosing. You gain a +1 bonus on attack and damage rolls. You gain a +1 bonus on saving throws. All your attacks are treated as magical for the purposes of overcoming damage reduction.
Level 6: You gain a +2 bonus on attack and damage rolls. You gain a +2 bonus to your Armor Class. You gain a +1 bonus on saving throws. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus. You gain a +2 bonus to two ability scores of your choosing.
Level 7: You gain a +4 bonus to one ability score of your choosing. You gain a +2 bonus to a second ability score of your choosing. You gain a +2 bonus on attack and damage rolls. You gain a +2 bonus to your Armor Class. You gain a +1 bonus on saving throws. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 8: You gain a +4 bonus to one ability score of your choosing and a +2 bonus to two other ability scores of your choosing. You gain a +2 bonus on attack and damage rolls. You gain a +2 bonus on saving throws. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 9: You gain a +3 bonus on attack and damage rolls. You gain a +3 bonus to your Armor Class. You gain a +4 bonus to two ability scores of your choosing and a +2 bonus to one other ability score. You gain a +2 bonus on saving throws. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 10: You gain a +6 bonus to one ability score, a +4 bonus to a second ability score, and a +2 bonus to two other ability scores of your choosing. You gain a +3 bonus on attack and damage rolls. You gain a +3 bonus to your Armor Class. You gain a +2 bonus on saving throws. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 11: Your weapons are treated as aligned for the purpose of overcoming damage reduction. You gain a +3 bonus on saving throws. You gain a +6 bonus to one ability score, a +4 bonus to a second ability score, and a +2 bonus to two other ability scores of your choosing. You gain a +3 bonus on attack and damage rolls. You gain a +3 bonus to Armor Class. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 12: You gain a +4 bonus on attack and damage rolls. You gain a +4 bonus to Armor Class. You gain a +6 bonus to one ability score, a +4 bonus to two other ability scores, and a +2 bonus to one other ability score. Your weapons are treated as aligned for the purpose of overcoming damage reduction. You gain a +3 bonus on saving throws. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 13: You gain a +6 bonus to two ability scores, a +4 bonus to one ability score, and a +2 bonus to two other ability scores. You gain a +4 bonus on attack and damage rolls. You gain a +4 bonus to Armor Class. Your weapons are treated as aligned for the purpose of overcoming damage reduction. You gain a +3 bonus on saving throws. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 14: You gain a +4 bonus to saving throws. You gain a +8 bonus to one ability scores, a +6 bonus to one ability score, a +4 bonus to two other ability scores, and a +2 bonus to one other ability score. You gain a +4 bonus on attack and damage rolls. You gain a +4 bonus to Armor Class. Your weapons are treated as aligned for the purpose of overcoming damage reduction. You gain a +3 bonus on saving throws. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 15: You gain a +5 bonus on attack and damage rolls. You gain a +5 bonus to Armor Class. You gain a +4 bonus to saving throws. You gain a +8 bonus to one ability score, a +6 bonus to one ability score, a +4 bonus to two other ability scores, and a +2 bonus to one other ability score. Your weapons are treated as aligned for the purpose of overcoming damage reduction. You gain a +4 bonus on saving throws. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 16: You gain a +8 bonus to one ability score, a +6 bonus to two ability scores, a +4 bonus to two ability scores, and a +2 bonus to one other ability score. You gain a +5 bonus on attack and damage rolls. You gain a +5 bonus to Armor Class. You gain a +4 bonus to saving throws. You gain a +8 bonus to one ability score, a +6 bonus to one ability score, a +4 bonus to two other ability scores, and a +2 bonus to one other ability score. Your weapons are treated as aligned for the purpose of overcoming damage reduction. You gain a +4 bonus on saving throws. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 17: You gain a +8 bonus to two ability scores, a +6 bonus to two ability scores, a +4 bonus to one ability score, and a +2 bonus to one other ability score. You gain a +5 bonus on attack and damage rolls. You gain a +5 bonus to Armor Class. You gain a +4 bonus to saving throws. You gain a +8 bonus to one ability score, a +6 bonus to one ability score, a +4 bonus to two other ability scores, and a +2 bonus to one other ability score. Your weapons are treated as aligned for the purpose of overcoming damage reduction. You gain a +4 bonus on saving throws. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 18: You gain a +6 bonus on attack and damage rolls. You gain a +6 bonus to Armor Class. You gain a +5 bonus on saving throws. You gain a +8 bonus to two ability scores, a +6 bonus to two ability scores, a +4 bonus to one ability score, and a +2 bonus to one other ability score. Your weapons are treated as aligned for the purpose of overcoming damage reduction. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Level 20: You gain a +10 bonus to one ability score, a +8 bonus to one ability score, a +6 bonus to two ability scores, and a +4 bonus to two other ability scores. You gain a +6 bonus on attack and damage rolls. You gain a +6 bonus to Armor Class. You gain a +5 bonus on saving throws. Your weapons are treated as aligned for the purpose of overcoming damage reduction. In addition, when taking a full attack action, you may make an additional attack at your highest attack bonus.
Now, some people are going to freak out. A PLUS TEN BONUS TO AN ABILITY SCORE BROOOOOOKEN. But let's be brutally honest here: that additional +2 doesn't mean much when you're losing the special properties on weapons and armor and lacking the potency and versatility of spellcasters. Even the 20% miss chance from a minor cloak of displacement will be sorely missed. I increased the bonuses available to the PCs to compensate slightly for their loss of magical items.
You may now discuss.
In this world, flying creatures (Harpies, Gianty owls, etc) become reallly dangerous as you can't fly? Bows help though.
I am working on a similar system, but it goes into more detail.
As an example healing will still be needed. Actually it will be needed a lot more since battlefield control spells, and and other damage prevention spells won't be available.
Many GM's do want to use the same monsters, but they don't like the Christmas tree affect.