When you open your brake system, there is a good chance that you will get air in the lines to other calipers that you have not opened up, so you must bleed the entire system.

If you use the pedal to bleed the brakes, you must be careful not to push the pedal all the way to the floor. In normal use, the pedal never goes all the way to the floor, and hence, the piston in the master cylinder never travels all the way to the end. In that unused portion, crud and corrosion usuallyl build up, and if you hit that area while bleeding, it is likeliy that you will ruin the seals on the master cylinder and shortly require a new one.

As other have noted, the Eezibleed is the way to go - pressure bleeding is much better for the system and does a better job, however, with new calipers, you WILL need a heavy plastic mallet to rap the new calipers while bleeding and knock loose air bubbles that adhere to the new bores.

Be sure to use the correct bleeding sequence. I believe that Ted gave you the sequence for cars with ABS brakes. If you do not have ABS and have the 'dual triangular' system, then the sequence is slightly different:

LR

LF (Upper) (Inner, then outer)

RF (Upper) (Inner, then outer)

RR

RF (Lower)

LF (Lower)

I usually bleed all untill clean fluid comes out, then bleed all a second time. Rap on new calipers each time.

If you have trouble getting flow from any caliper, release pressure from bleeder, remove bleed screw and carefully clean bleeder and caliper hole with fine wire.

If you have trouble with flow at rear calipers, have assistant pump pedal halfway while pressure bleeder is in place - sometimes the rear pressure relief valves (sort of an early rear wheel anti-lock device) collect a lot of crud if system had not been flushed regularly and it can block fluid flow.

If this does not return good pedal, then check all brake hoses for signs of age - they could be 'balooning'. Also, it is possible that your master cylinder is failing. Note that with new pads, particularly with old rotors that have not been machined, or if you have used one of the rubbery anti-squeal substances on the back of the pads, there may be some 'give' in the pedal that will feel a bit like a soft pedal. Normally this will go away after the pads have worn in to match the rotor surface and you do a couple of good hard brake applications.

It is good practice to allow the pads to wear in gently for a hundred miles or so - no heavy applications. Then, do several 60 - 0 hard stops to heat the pads up to the point that you can smell them. This drives out the solvents used during manufacturing and will help prevent future glazing of the pads - they will work better during their life.