Paper, margins, units and layout

Useful imports for geometry/style examples:

import com.nsdev.lettergenerator.model.layout.Bounds;
import com.nsdev.lettergenerator.model.layout.Margins;
import com.nsdev.lettergenerator.model.layout.PageSize;
import com.nsdev.lettergenerator.model.layout.PageSpec;
import com.nsdev.lettergenerator.model.style.Style;
import com.nsdev.lettergenerator.model.style.TextAlign;

Setting	Default	Customization
Paper	PageSize.A4, 210 × 297 mm	page(PageSize.LETTER), 215.9 × 279.4 mm
Margins	20 mm on each side	marginsMm(15) or margins(new Margins(top, right, bottom, left))
Header content height	25 mm when present	headerHeightMm(...) or exact header bounds
Footer content height	15 mm when present	footerHeightMm(...)
Body/header and body/footer separation	5 mm	Advanced PageSpec for complete zone control
Body paragraph spacing	3 mm after paragraphs	style(Style.builder().spaceAfterMm(...).build())
Text size	11 pt	fontSizePt(...)

Margins constructor order follows top, right, bottom, left:

var letter = Letter.builder()
    .page(PageSize.LETTER)
    .margins(new Margins(15, 18, 17, 22))
    .body("Custom stationery")
    .build();

Page/box dimensions and spacing use millimeters. Font sizes use points. A line-height value is a multiplier, so 11 pt with 1.2 gives a 13.2 pt line box. Rotation uses degrees and opacity uses a value from 0 to 1.

The margins form the inner page. Header/logo content occupies a reserved top zone, footer content occupies a bottom zone, and the body flows between them. The library reserves each zone’s full width; text does not wrap beside fixed elements. Empty fluent header/footer regions reserve no space unless advanced fixed elements use those zones.

PageSpec.A4 and PageSpec.LETTER are immutable advanced-model presets with default margins and zero reserved zones. Letter.builder() creates the zones needed by its header/footer calls. This difference matters when constructing LetterDocument directly.