Puffin should automatically download a file when prompted.
You may force Puffin to download a link by long-pressing on the link and selecting Save Link. The file can be saved in your device, on Google Drive, Dropbox or OneDrive.
To check the download status of a file, go to the Main Menu, and click the Download icon.
To access a file on your device, tap the completed download from the list. Then, you can choose other compatible apps to open the file.
To access files in your Google Drive/Dropbox/OneDrive, you need to use apps from Google Drive/Dropbox/OneDrive.