How it works:

1. User works as usually with his ERP or other system
2. SimpleInvoicer takes business documents from ERP (or other any data source), creates PDF and UBL documents.
3. Signs both document
4. Sends via E-mail, FTP, Web Service or any other way
5. SimpleInvoicer on receiver side checks signatures and UBL validity
6. User imports UBL 2.x document into his ERP or any other system also his able to view Signed PDF or print it