CD74HC125E, resistor or not resistor?
Check the datasheet for Absolute Maximum Ratings.



For normal use you want to look at: 


  DC Output Source or Sink Current per Output Pin, IO
  
  For VO > -0.5V or VO &lt; VCC+ 0.5V
  
  ± 25mA


Keep well below that value, say 20mA max, then you are safe. You'll have to calculate a series resistor for that as the device will be fried if you exceed the maximums.




The other currents mentioned are important when the input or output is pulled higher or lower than its own power supply rails, which in most cases is a situation you want to avoid. Look closely at the conditions on every second line eg.: For VO &lt; -0.5V or VO &gt; VCC + 0.5V