The gradient above is clipped to the exact shape of the glyphs themselves
(background-clip: text) instead of painting across the whole heading’s box - the
standard technique for gradient-filled headings, paired here with color: transparent
so only the background shows through the letterforms. The third heading’s gradient starts from a
translucent stop, so it fades in from the left (it follows transparent text, which once made a
translucent gradient like this vanish).
Unlike PeachPDF’s SVG gradient-text support, this paragraph and the headings above it all stay ordinary, selectable, extractable PDF text - try selecting this text in a PDF viewer. Only the background paint is clipped to glyph shape; the text itself is never converted to vector art.