To fulfill the requirements of the efficiency and security in the paperless era, Taiwan is currently implementing XML[1] format electronic invoices with digital signatures. Although XML[1] documents are beneficial to standardize information exchange, the portability, visual viewing and signature authentication of those still have room for improvement. In our implementation, we use PDF documents with digital signatures as electronic invoices. Thanks to the wide spread of PDF reader software and its better graphic interface of signature verification, users can easily read and intuitively authenticate the sources of documents. Our implementation involves five techniques. The first one is a technique to convert volumes of data between two heterogeneous databases. The second one is a technique to rapidly transform normal documents into digitally signed PDF files. The third one is a technique for solving several difficulties when Chinese characters are encountered during document conversion. The fourth one is a technique for generating digital signatures through the Adobe Acrobat certification API combined with a hardware security module (HSM). The fifth technique is to supply a status board which can display system operation status. With this function, users can confirm if the PDF e-invoices process has been completed or not. The board also displays the status of execution of each phase, and updates the value of table fields in database. Finally we will remove the unnecessarily file directory so we can use the space of the disk effectively. We have already developed a system with the ability of issuing a great deal of digitally signed PDF e-invoices. This system now is providing enterprise e-invoice notification service for Data Communications Business Group of Chunghwa Telecom. In the future, this technology can be utilized on various value-added applications including electronic bill/receipt services, electronic notarization services, digital certification, and multi-entity electronic contracts.