Format is not only important for beating an ATS, but also for attracting – and maintaining – the gaze of a recruiter. Your resume should be neatly formatted with appropriate section headings (qualifications, experience, education) which allows an ATS system to track relevant data.
Likewise, your resume should be formatted in a Microsoft Word document. ATS systems are advancing and becoming more capable of scanning PDFs, but there is more opportunity for sections of a PDF document to be missed during the scan.
Moreover, once you get your resume passed the ATS, you want to make sure that you can hold the attention of a recruiter, who spends an average of six seconds deciding on whether or not your resume marks you as a viable candidate for the vacant position.