Lower the action of dreadnought guitar
Things you needed:
Pencil
Pentel Pen or Marker
Ruler
Sandpaper
File
Clean cloth or paper towel
Brush
The first thing you need to do is either you remove the strings if you intend to clean your guitar and put on a new set of strings or if you just put new strings on and forgot to adjust the height of your strings, all you need to do is loosen the strings as much as you can then carefully remove the bridge saddle.
Once the saddle is removed, use the ruler to mark it as to how much you're going to sand it down. Put a line using the pencil as your guide as to how far you're going to sand it down. Then use the marker or Pentel Pen to mark the bottom of the saddle to know if you're sanding it evenly. And when you're doing it, do it gently and keep on checking how far you're going. Then use a file to smoothen the area.
Once you're happy or near your target line as to how much centimetre you want to remove, brush the area off or wipe with a clean cloth and put it back. Then check if you're happy with the height of your strings. Note that it is not advisable to sand it down too far and make the strings too low because it will be prone to buzzing and you wont be able to reverse it. So it's better to just sand it down little by little. Also the string pull is great when it's a bit high. So, limit it to 1 cm or less when you lower the action of your guitar.
Put saddle back and try to tune it and play the guitar. Even though you lowered it a centimetre or less, you will still feel the difference. Hope this helps.