Compile the small app below. It loads a simple SVG file to a QPicture (to hold vector data). This 1st SVG file has a text and a text that is converted to a path. Rendering to pixels (QWidget, QImage) works fine. Rendering to SVG or PDF (Qt print engine) adds a stroke around the paths (see the out.***).

This behaviour becomes clear if you change the line
QSvgRenderer svgRenderer(dirPath + "in1.svg");
to
QSvgRenderer svgRenderer(dirPath + "in2.svg");
In this 2nd example SVG file is just a line and a rect, both with 1 pt thickness. After qt's conversion the line is fine but a stroke seems to be added to the the rect.

It seems like someone forgot to clear the pen with QPainter::setPen(Qt::NoPen)?