The first rule of resumes is always send it as a PDF. Always, always, always send it as a PDF. It preserves your formatting while Microsoft Word/Apple Pages versions may not.
The only exception is if the ATS requires you to submit it as a Word Document. If the resume submission portal requires a Word document, obviously give them a Word document. If you are using Google Docs to make your resume (which is my personal preference, you can find my template here), you can easily download your file as a .docx (aka Microsoft Word format) by following these instructions here or here.
Your resume PDF should be titled Firstname Lastname – Resume. Resume reviewers often see the file name so don’t look bad. “Firstname Lastname rez”, “Firstname 1(1)”, “FIRSTNAME LASTNAME RESUME” and “Firstname Lastname – Resume (Data Centers)” are all sloppy and make you look bad.