Select Trim Leading Whitespace in the Extra menu to remove whitespace from the start of each line. If you selected part of the file, only the selected lines are trimmed. If not, all lines in the file are trimmed.
If you’ve made a rectangular selection, EditPad Pro only deletes whitespace inside the rectangular block. Whitespace in the leftmost selected column and adjacent columns to the right is deleted. This whitespace needn’t be at the start of the line
Extra|Trim Trailing Whitespace
Extra|Auto Trim Trailing Whitespace