Hi!
I highly suggest to Download the file as PDF Before Printing as this will lock fonts, margins and layout. In Word Online: File → Save As → Download as PDF. You need to check as well the margins. In Word Online, go to Layout → Size & Margins. Make sure size matches your printer default (Letter vs A4).
Note: Avoid Browser Print
Don’t use the browser’s Ctrl+P → Print.
Instead, always use Word Online → Print → Open in Desktop App or PDF.