Downloading and installing fonts has nothing at all to do with whether you have a trial version. Fonts are installed at the OS level, or in the Adobe private fonts folders. That said, downloading fonts from a friend is almost certainly a violation of the font licensing.
Ok thanks for replying. Didn't know what. Where can I buy Sabon Bold from then and install it to my Indesign trial?
You can purchase the font from Linotype, Fonts.com, MyFonts.com and other reputable font distributors.