You can work with Billdu apps even offline, there are however some limitations:
With our mobile apps you can create invoices, estimates and other documents
Documents will not get numbers automatically. Those numbers will be added later when connected to the internet again or you can add a number manually. Edit the document and select Details. Don't forget to check the numbering settings after a manual adjustment when you're online again.
eCommerce and Appointments apps work offline but some features (e.g. assigning team members) will not be available