Hi and welcome,
Check to see if you have this font installed,
(Franklin Gothic Book) look here specifically for the Apple one (/Library/Fonts/FRABK{,IT}.TTF).
If you do have it then try this, but first run a full TM backup, once done delete the font. If all is ok with iWork do not reinstall it, but if the crashes continue then you can replace it from the backup, because possibly it is the issue.