CoughDrop is connected to the cloud, so any changes you make to boards are automatically saved and backed up the next time your device syncs. That way you don't have to worry about whether you've manually backed things up, and you can access the same boards for the same user across multiple devices.
Sometimes, though, it's still useful to be able to download a backup of boards you have created in CoughDrop, either for backup or to share with others. CoughDrop uses the Open Board Format as its standard file format, which is an open-licensed file format meant to allow importing and exporting boards across different tools and devices.
You can download your board set at any time by going to your home board and exiting Speak Mode. Then hit "More" in the board menu and then select "Download Board".
If the board has no links then it will start downloading automatically. If the board links to any other board then CoughDrop will ask if you want to download just the current board, or also all boards that it links to. Either way, the download will be a single file. Single boards end in the .obf extension, while board sets end in the .obz file extension.
Once the download is finished you'll see a link to download the board. You can hit the link to download it to your device for whatever use you have in mind. Keep in mind that the file download link is only valid for about six hours after its created.