Note that this support is soon to be deprecated in favour of linking files via Files app.
Although Texpad iOS has for some time supported Dropbox storage within its app folder in Dropbox at Apps/Texpad, this support is being deprecated in favour of access via iOS Files app.
Dropbox storage requires a Dropbox account and working with files stored in your Dropbox folder requires internet connection. Texpad can access all files inside Apps/Texpad folder in your Dropbox. See below for more details on linking Texpad with your Dropbox account.