Can you get air in lines changing shoes?

the67fish said
No way for air to get into the system just by changing brake shoes. If the pedal is low then the shoes might need adjusted out some.

This ^^^

I just went through this on my Wife's 73 Mercury Comet. I did a complete brake job and after putting it all together had a spongy/low peddle. I adjusted the rears up again, and voila, nice peddle.