https://forum.support.xerox.com/t5/FreeFlow-Core/Where-to-add-fonts/m-p/201433 This link has the information you are looking for.
This may work. When saving as PDF from Word, select options, then check save as PDF/A (see below).
Try one of the two locations:
Reboot the server or restart the FreeFlow Core service after adding the fonts.
We use Proxima Nova font as a preferred font. With conversion/distilling from Word to PDF, the font is substituted. It does no good to have any settings in FFC to address any embedding or substitution of this font, cause it is already substituted by that time. Where does the Word to PDF coversion or distilling look for for fonts? Where would we install this font on the FFC server so this is used?
Here is the error log from FFC:
****** Convert Warnings ******
1 font(s) are missing and substituted:
Proxima Nova Regular => Candara