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