My colleague recently acquired an iPad and in setting up her iPad she ran into a problem that is quite common. While you can open a file from the Dropbox app into Quickoffice (or other apps) you cannot upload it to Dropbox from within QO until you add DB to QO. Once you have done that, the best practice IMHO is to open the file from DB in QO and edit it there. QO will then automatically save that document back to DB. A few screenshots should help clarify.
First you need to connect QO to DB. You do this from within QO:
Once you have clicked the “+” symbol you will get this menu:
Notice that you can add accounts from several different services including Evernote and Google Docs. The next step is to fill in your credentials.
Now, when you want to edit a file that is saved in Dropbox (or one of the other services) simply select it from the account listed in the left hand column.
QO will periodically automatically save the file to your DB account. Now that your DB account is set up you can also save local files to DB by using the “Save as” menu, navigating to the DB folder where you would like to save it.