Toni Bowers outlines some issues with resumes formatted in Microsoft Word and those converted to PDFs.
A lot of people spend time formatting their resumes with eye-catching charts, tables, and graphs. Honestly, this can be a mistake for several reasons. One is that the information in your resume is important, not how it looks. In fact, excessive formatting can actually detract from the message.
Also, if a resume is formatted in one version of Microsoft Word, for example, you can't be sure the person looking at your resume has the same version. Your formatting could be stripped out anyway.
Some people convert their Word files to PDFs to avoid the version incompatibility issue, but even that can cause problems, because many companies and recruiters use applicant tracking systems (ATS). ATSs are keyword-searchable databases that allow companies to store information about candidates that have submitted resumes. A lot of times, PDFs don't convert well into these systems. Instead of searchable text, they convert in to indecipherable images with no discernable text.
This means the chance of your resume being seen has been lost. Newer applicant tracking systems are doing a much better job at reading PDF conversions, but you have no way of knowing if the company you're applying to is using a new version.
Also, recruiters often have to copy and paste information from a resume into a new format that follows their protocol before they forward it to a hiring manager. They can't do this with a PDF if it is a Word doc that has been scanned. (Copying and pasting is possible if the Word file is saved as a PDF.)
I'd suggest using Rich Text Format for your resume, and be sure you use lots of specific keywords so that ATSs or the eyes of a harried HR recruiter can catch them easily.