If it's not many, we suggest using Open In... to move files into the new app. The limitation there is that you can only use Open In... for one file at a time.
If you have a full Library of documents, you will want to start by transferring your files and folders to your local computer by using the Send to iTunes command. Once your files are moved into iTunes, you can sync them to the cloud to one of our four supported cloud platforms. All of our supported cloud platforms (Dropbox, OneDrive, Box, Google Drive) have desktop apps that will create a synced folder on your computer. Once you have that folder, you simply need to drag the files and folders from iTunes File Sharing into the synced folder.
Once that is done, create a connection to that cloud service and you will see all of your documents ready to go.