Pinterest does not let you pick a font for your profile or board names, but you can paste special Unicode characters that look like bold, italic, script or outlined letters. This generator converts your text into those characters. They are real text, so they copy and paste anywhere that accepts Unicode, including your Pinterest display name, bio and board names.
Use them sparingly. These are mathematical and decorative symbols, not ordinary letters, so screen readers may read them out letter by letter or skip them, and Pinterest search will not match them to normal words. Keep important keywords in plain text and use a fancy style for one decorative word or a short heading.
Accessibility and search: the trade-off
Fancy Unicode text looks like letters, but to software it is a string of symbols such as "mathematical bold capital L". Screen readers used by blind and low-vision people may spell these out or skip them entirely, which makes a whole bio unreadable for them. Search engines, including Pinterest search, generally treat them as different characters from normal letters, so a board named in script will not show up for the plain word.
A good compromise is plain text for anything people need to read or search, plus one styled word or a text divider for decoration.
Want a real font on your pin images?
This tool is for text fields. For the text on a pin image itself, you can choose from proper web fonts in the add text to image tool or the quote pin maker, which are readable by everyone looking at the picture.