You can open documents in Dropbox with Office 365 Online, for example, in Word, PowerPoint, and Excel.
1. Go to Dropbox Webview by logging in to http://dropbox.com.
2. Click on the folder you would like to open, for example 'test share'.
3. Click on the file you would like to open, for example 'test document'.
4. The document will open in your browser. In the top right hand corner click 'Open', and select 'Open in Microsoft Word Online'.
5. Microsoft Office will take you to this page. Click 'Allow' to access the specific file you would like to open.
6. If you see this message, click 'Sign in with a work or school account'. You may need to login by typing your email/username and password.
7. You can now edit the document in Microsoft Word Online (or any other Office 365 program relevant to the file).