GumPad uses OpenType fonts that ship with Windows. You can change these defaults by installing other fonts and setting up GumPad to use these other fonts. These can be changed from the Preferences->Fonts menu item. In addition, you can set the font of text selected in GumPad from the Format->Font menu item
The following links point to sources of Indian language fonts that can be downloaded and installed in Windows. These links open in a new browser window/tab.