Hi there

Welcome to the Box Community, I'm happy to help!

You should still be able to edit your office files even if you do not have a paid MS office paid subscription. In fact, if are a free Box user, you can use the integration even without a Microsoft Office Online account.

To learn more about the Box for Office integration, please take a look at this article: https://support.box.com/hc/en-us/articles/360044196433-Box-for-Office-Integrations#h_3fecec92-f129-4920-aba3-d6eb54123de6

Thanks for posting and let me now if you have questions!

All the Best,