HTML to PDF using flying saucer: bold text is blurry

Question

I am using flying saucer (xhtmlrenderer) 9.1.22 to create PDF files from HTML content,

but the bold text in PDF looks blurry.

this is my code snippet:

ITextRenderer renderer = new ITextRenderer();
renderer.getFontResolver().addFont("arial.ttf", BaseFont.CP1252, BaseFont.EMBEDDED);
renderer.setDocumentFromString(htmlAsString);
renderer.layout():
renderer.createPDF(output);