Petrus was appointed to the School of Business Bundoora in January 2003. He returned to studies in July 2000 after having worked for almost 10 years in accounting roles in Jakarta at Indonesian Satellite (Indosat) Co. Ltd, ConocoPhillips Inc Ltd (was known as Gulf Canada Resources Ltd, HQ in Calgary, Canada) and Astra Financial Services. He initially graduated from Diploma 3 Akuntansi (Diploma in Accountancy) at Universitas Indonesia, Jakarta in 1991.
Having completed his Postgraduate Diploma in Accountancy at La Trobe University in July 2001, Petrus continued his study to Master of Commerce by research and worked as research assistant and casual tutor at the School of Business at Bundoora campus during 2001 and 2002. By August 2002, his masters program was upgraded to doctorate level. His PhD specialisation is accounting information systems (AIS) and enterprise resource planning (ERP) systems. In January 2003, Petrus was appointed as associate lecturer at the School of Business at Bundoora and taught a first year Accounting subject, while working on his PhD at the same time. In July 2006, Petrus joined the Regional School of Business in Mildura and started working as Accounting lecturer and researcher.
Petrus has successfully completed his PhD in April 2007. His research was a collaboration of two disciplines: accounting and Information Technology (IT), and was applying the human-centred principles in designing AIS. In his PhD thesis, he examined a broader perspective of the human-centeredness of AIS as part of the Enterprise Resource Planning (ERP) systems. Petrus returned to Bundoora campus in early 2014 and started teaching in the business intelligence area.
Since 2006 Petrus has been working pro bono as accounting adviser and auditor for the Nusa Tenggara Association (NTA) Inc., a Canberra based not-for-profit non-government organisation (NGO) committed to supporting projects in the Indonesian islands of West Timor and Florest in the East Nusa Tenggara Province - the poorest region of Indonesia and amongst the poorest in the world. Since January 2013 until June 2015 Petrus was appointed as member of the Code of Conduct Committee of the Australian Council for International Development (ACFID) in Canberra and since then has been actively supporting the Financial Review Standing Committee.