There are two ways: first, just enlarge the font. If a piece of A4 paper has one word, taking Song Style as an example, you probably need to set the font to 600.

Second, when inserting wordart, insert one word to be printed at a time. Then drag the font to the whole page. The specific method is "Insert"-"Picture"-"WordArt". After inserting the font, hold down the lower right corner with the mouse and pull it to the size you want. Personally, I think the second method is better. Because you are using the default font.