SVG is a vector-based format that can be inserted into WORD, and maintain it's crisp vector lines. If the WORD file is exported into a PDF correctly, then the figure remain perfectly crisp in the PDF.

There are lots of options for saving SVG formats from Adobe Illustrator, and some choices are not well compatible with WORD, so it's important to do it right. Here is a video showing what I find works best:

Here is a screen capture of the export settings I show in the video:

In the video I mention that there are limitations to the complex features of your image that will work in an SVG or word. Read more about those limitations.

Now that you have your SVG files, here are tips for inserting them into Word.