During a Webex meeting, you can share not only your screen but also individual files. When you (1) click the Screen Share icon, you’ll be presented with a gallery of options that includes uploading a file.
However, it can be hard to find! Usually, it’s the first option in the very bottom row (2), so you’ll have to scroll down to see it.
Further Reading
Webex has a very detailed guide on sharing content during meetings. You may find it helpful if you’re going to share other types of content besides files.