The first section of the trail is a flat jaunt through the woods.  As the trial turns west, however, it starts to get a little rougher.  You'll pass Dorr Mountain South Ridge Trail(from which you will be descending on the return) on your right after a little over a mile.  A tenth of a mile later, just past a pretty waterfall, you'll encounter the A. Murray Young Trail on your right.  Here you have to cross Canon Brook and climb some stone steps to the left.  The trail gets much steeper as you parallel the cascade up the side of Cadillac.  This is one of the more strenuous sections of the hike, made easier since it's early on.  You'll cross back and forth over the Canon Brook on some pretty sheer rock faces.  You'll eventually get back into the woods and after about 1.8-1.9 miles you'll arrive at Featherbed, a pretty little pond with a nearby bench to take a rest upon.

Once you've caught your breath, hang a right and head up Cadillac.  The ground here is pretty open and you get good views to both the east and west.  The trail tries to skirt you around Cadillac Summit Road as much as possible, but you'll still see and hear signs of automobiles as you climb up.  The grade is pretty forgiving here, making for a pretty relaxing climb.  After about another 1.2 miles, you'll hit the summit of Cadillac and all the people and cars that entails.  A good time for a bathroom break and to refill any water bottles.  The trail to Dorr starts from off of the main summit loop path where people congregate, but it is as well marked as all trails in Acadia are.

The path down Cadillac's east face to Dorr is quite steep, but thankfully it does so in a series of switchbacks to keep it manageable.  In addition, you hit the gorge between Cadillac and Dorr near its highest point, so neither the descent or ascent are out of control.  In about 0.6 miles you'll be at the top of Dorr mountain, looking back at all the people on Cadillac.  

Now turn south and head down the 1.3 mile South Ridge Trail.  The descent is long and gradual, with few abrupt changes.  When you hit Canon Brook Trail hang a left and head back to your car.