It may help you to understand the Achilles tendon pain if you look in Google images for the Achilles tendon. You will also find many other pictures of the muscles and tendons in the foot. In my opinion, a person should be careful with any pain in these areas and reduce the mileage or take rest days until the pain goes away.

I used to try to adjust my walking to prevent pain, but that never worked. When I gave the task to my subconscious and ignored walking technique, I stopped having as many little pains.

Many inexperienced hikers tend to overstride, especially uphill. This can lead to various injuries. By overstriding, I mean the heel placement is forward of the body's center of gravity when the foot touches.

There are many experienced backpackers here who hike long miles. They didn't get that way in a year or two. I suggest keeping the miles down the first year while taking your time to enjoy the scenery or stopping for a cup of coffee.

If you are significantly overweight, you may have to work on that before you can start doing longer miles.