Create PDF form fields with set text size for copied and pasted text

I'm creating a fillable PDF form in Acrobat. The form fields have been set to a specific font size (Helvetica size 10) by going to prepare form > text field properties > appearance. When someone types new text into the form field it displays correctly (Helvetica 10) however if someone copies text from Microsoft Word and pastes it into the form field it displays way too big and no longer uses the set font size. How can this be fixed??

(My client does not want the scroll feature on these fields because they need to be able to see all text when the completed form is printed. They need to make sure users have enough space to provide their responses and this font sizing issue with copy/paste means users cannot paste in all their content (vs if they typed it directly into the field it would fit.) Thanks in advance for your tips!