How can ruler be used to change margins?

To change margins using a ruler, first ensure that the ruler is set to the appropriate measurement units (inches or centimeters). In a document editing program, place the cursor on the left or right margin area, then adjust the margin by dragging the corresponding margin markers on the ruler to the desired position. For top and bottom margins, you can typically find similar markers on the vertical ruler, if available, or adjust them through the page setup settings in the software. This visual method allows for precise control over the document's layout.