Not all computers or operating systems have the same default set of fonts installed. Because LayOut doesn't embed fonts into its files, all fonts used in a LayOut document must be present on the computer you're using. If the font in question isn't present on the computer, text in the LayOut file will appear in another font.
If you know which fonts are missing, try doing a Google search to locate and install the font on your computer. You can find more information about installing fonts by visiting the Microsoft or Apple support sites.