You have always been able to access Google Drive files offline with the official desktop client "Backup & Sync", but considering how awful this program is, it's nice to see that the web application has similar features. Google has added the ability to select Docs files for offline access (and edit them offline) earlier this year, but now you can save any Drive file.
"You can already make Google Docs, Sheets and Slider files available offline, the company wrote in a blog post." Now, as part of a new beta, you can also mark PDF, Image, Microsoft Office and other non-Google files for offline access with Google Drive on Chrome. "
The feature is currently limited to G Suite organizations that have opted in to the beta programs for File Stream and offline access, as well as for regular Gmail accounts when offline access is enabled, but the rollout may not be complete. Annoyingly, the functionality is still limited to Chrome – as much as Google doesn't like to confirm it sometimes, still there is Firefox.