PDF file size too large

I have an 8-page PDF fillable document with a file size of 28,998 KB. I can't email it or upload it because of how huge it is. When I perform the Audit space usage, it says that the font is 99% of the file size. The primary font in the original Word document was Calibri and converted into a PDF fillable as such. How do I choose a "smaller" font and is it possible for me to edit or convert the PDF fillable without going all the way back to the original Word document and starting all over?