A margin is a working space

Margins give a page more than an orderly border. They separate a line of text from the surrounding room, allow a hand to hold a book and give the reader a place to pause. A narrow column can feel calmer than a full-width block even when it contains the same words.

For a short printed note, begin with the reading distance. Choose a comfortable text size, then adjust line length and spacing together. Print a sample rather than trusting the screen alone; paper changes contrast and apparent scale.

Decoration should support the reading order. If a heading, caption and paragraph all compete for attention, remove an emphasis before adding another.