Since the Covid-19 pandemic started, seminar documents at the Department of Informatics Engineering, UIN Sultan Syarif Kasim Riau, have switched from papers to PDF files. To create a certificatebased digital signature, lecturers use desktop-based PDF processing applications or an Android application developed in the previous study. Unfortunately, lecturers who own iPhone does not have an application with similar functionality. The problem is that the Swift programming language for iOS does not support signing PDF files with digital certificates, and third-party libraries are costly. Therefore, this research develops a digital signature system model with web services for signing on the server side. The results of black box testing on web services and its mobile client application meets the requirements stated in the software requirement specifications. The User Acceptance Test results show that the digital signature system meets the user’s needs.
