A question asked on the ProBoards Support Forum may be helpful. I have copied it below. And to be even more helpful, I have also copied the reply!
When modifing a skin what are the available fonts to use.
Any font is available, but it's only suggested to use common fonts that are on the majority of computers. If you download a font and then set that font as the font of your forum, most people won't be able to see it as they should. Instead, their browser will switch to a different font to substitute it.
As you suggested, you probably don't have the alba font on your computer. For that reason, it may be as well to avoid using alternative fonts.