The pushrod needs to almost touch the piston in the back of the master cylinder so you can extend it until it does touch the back of the piston & just shorten it a 1/4 turn or so , the pushrod is 2 pieces threaded together so you can hold one end & unscrew it , if the pedal has always been low this could very well be the problem from before you owned it . you can put a felt pen mark on the tip of the pushrod to see if it is touching if you cannot feel it as you slide it into place , often it is easy to start with the pushrod too long , if it is too long the brakes will not release properly once the pedal is pushed .
to adjust the shoes you need to adjust them out with the star wheel inside the drum until they touch the drum & hold the self adjuster out of the way back the brakes off 3-4 teeth .