Zooming in and out on Word documents is easy. However, Word does 'remember' these settings, so any new documents you create or open should display with your last-used View and Zoom settings.
Unfortunately, Microsoft does not currently let you modify or save Zoom-level defaults. How to change font defaults in Microsoft Word 2016 for Windows For more details on how to customize Word's font settings, read: You should note, however, that zooming is different than merely increasing or decreasing font size. Word's View options let you zoom on pages, so the documents themselves get larger or smaller, and you can fit multiple pages into a single screen for more effective navigation. Or if you have super vision or for some peculiar reason just really enjoy working on tiny pages, you can also zoom out accordingly.
If you use a large external display or just don't want to have to squint at the page, you may want to zoom in. When you first get started with Word, all of your documents, new and old, open at the app's default View settings: Print Layout at 100 percent Zoom.