Since version 2.8.6 you can import up to 20 TrueType or OpenType fonts to the app (only 1 custom font in the free version).
Just copy your font files (extension .ttf or .otf) to the folder “addwatermark/custom_fonts” on your device. This folder is automatically created after app installation.
When you start Add Watermark, you can see now the custom fonts (Settings / Text / Font), added to the build-in fonts starting with numbers ..:
Please note, if you can’t see a custom font in the app, the file might have a wrong format or is corrupted.