Mary is right. Breed isn't as important as conditioning, training and being a responsible handler.
Knowing that you're going want to take your dog in the back country is the first in a line of considerations for selection. Temperament, agility, and size will be important for how you'll live day to day with your dog. Working dogs, from Samoyeds, Malamutes and Huskys to Border Collies, Kelpies and Aussies (and everything in between) are excellent for packing and can be great family dogs. The working breeds are numerous. They need lots of attention, exercise and thrive on having 'jobs'. They may or may not fit into the rest of your lifestyle. But on the packing side, the larger the dog, the more food they'll need.
Whether you choose a working breed, a sporting breed or an Evolution Dog (aka Mutt), training will make the difference in your (and others') experiences on the trail. Start early and be diligent with obedience training. Find a good professional trainer to help teach you to be a good handler. DON'T work the dog off-lead until its REALLY ready. Be patient. The rewards will be worth the work.
If you plan on having your pup carry a pack, get it early, but don't put any weight in it until they're a year old. You can start before then with just paper in the pack to let them get used to it. They can carry 1/4 their own weight, but shouldn't carry any until they're 12 mo. old. Wolf packs makes some great packs designed for working dogs (www.wolfpacks.com) but there are lots of companies that make them. I've had a WP Bandito for my dog since she was about 6 months old. After 4 years of use in the Sierra high country and foothills (read granite & brush) it shows little wear & tear.
Toughening up pads can be harder than it seems. I run mine on pavement next to my bike and she's still gotten tender hiking long periods on granite in the high country. Consider having your pup carry a set of MuttLuks (www.Muttluks.com) or other boots in their pack just in case. (If your pup has dewclaws, check that the strap for the boots doesn't run across the dewclaw, this can cause irritation or a wound.) I helped some people extract their 115# Rottweiler out of the wilderness with a bad case of couch paw once and would hate for any dog to go through that. (This is another good reason to consider size). The pup's pack should also include some basic first aid.
Most importantly, take every opportunity to expose your puppy to new places, new dogs, new people, different situations. Socialize them early and often.
Be responsible on the trail. In areas of heavy use, observe leash regulations, even if you believe your dog is well behaved and can handle being off lead. Sometimes its a drag. While working as a wilderness ranger in a heavy use area, I was charged multiple times by dogs off-lead in an area where leashes were required. In every case the owners swore the dog was a 'nice dog' etc. etc. Even 'nice' dogs will get protective in strange situations with strange people and unfamiliar territory.