Images, logos, SVGs, PDFs and custom fonts live in the project folder, next to every other project file. Add them from the Project Editor (drag them in, or Add Asset). A block uses one by name: assets:logo.png for an image, or a font's family name for font_family.

Which font wins

For a block's font_family, the first match of:

1. A .ttf or .otf in the project folder.
2. A global fonts folder shared by every project: drop files into Yatate/fonts in your OS's app-support directory (there is no screen for it).
3. One of the app's built-in fonts, below. They are case-insensitive.
4. The PDF library's default font.

Only normal and bold weights are used. A custom font named like a built-in one wins for that project.

Built-in: Cousine, IBMPlexMono, FiraSans, Lato, PTSans, TitilliumWeb, AlexBrush, Allura, GreatVibes, MrDeHaviland, Parisienne, Sacramento, CrimsonText, IBMPlexSerif, PTSerif, Spectral, Kalam, Pacifico. The script families (AlexBrush, Allura, GreatVibes, MrDeHaviland, Parisienne, Sacramento) are also what a signature field's Type mode offers.