Enable font hinting
To adjust the display of an outline font (learn more about font hinting) when rendering PDF documents into image GroupDocs.Viewer provides setEnableFontHinting() setting as shown below:
NOTE: this option is supported when rendering into PNG and JPG.
try (Viewer viewer = new Viewer("sample.pdf")) {
PngViewOptions viewOptions = new PngViewOptions();
viewOptions.getPdfOptions().setEnableFontHinting(true);
viewer.view(viewOptions);
}