Since 2.0.20 we have rendering issues for PDF's with bitmapped fonts. Please see attached images, the 2.0.19 and 2.0.20 version. Both are rendered from a A4 PDF on 300 DPI. Font size is around 12 points I think.
A PDF with the problem and a diff image is attached.
I think it is related to
PDFBOX-4516 (which is generally a great improvement).