Dropbox for Android has been updated to add document previews, along with smarter searching. Word Documents, PowerPoint presentations, and PDFs can now be viewed directly in Dropbox for Android, rather than moving you to a different app.
Search has also been improved in this update. In addition to searching your entire Dropbox for a file, you can now search individual folders. The app will also track your recent searches, and will also try to predict what you're searching for as you're typing. Dropbox will highlight filenames that match your search criteria.
This update also allows you to set view-only permissions on shared folders, which was previously only available to Dropbox for Business customers as an early beta. This Dropbox for Android update is rolling out on Google Play Store right now.