How to use custom font in WinRT RichTextBox control?
In SfRichTextBoxAdv control, you can use any custom font to render text contents apart from the fonts installed in your machine.
Add the required font as a resource file in your project.

You can use the custom font by specifying the font name with its reference path and “#” as prefix.
The following code example demonstrates how to use custom font in SfRichTextBoxAdv control.
XAML
<RichTextBoxAdv:SfRichTextBoxAdv x:Name="richTextBoxAdv" FontFamily="Assets/MyFont.ttf#MyFont" />
The following sample demonstrates how to use custom font in SfRichTextBoxAdv control.
WPF: Sample_WPF
UWP: Sample_UWP
WinRT: Sample_WinRT