When copying text from a printed PDF from QtWebKit the font size and font is not the same as expected

When copying text from a printed PDF from QtWebKit the font size and font is not the same as expected. In the example the font size changes from 12pt to 14.5 pt and font family from Calibri to CalibriRegular. When using CalibriRegular in the HTML file, the result font family changes to TimesNewRoman.

This only happens when it comes from QtWebKit and seems to be down to the font being used when rendering which is then passed on to the PDF