You should upload your resume as a PDF or Doc depending on what format the employer asks for. Both of these formats are commonly used for job applications, but different employers might have different preferences.
If the job ad says you should submit your resume as a PDF, then submit a PDF. If, on the other hand, the employer requests a DOC, then make sure you submit a DOC file. Using the right file format will help you make a good first impression because it shows that you read the job description carefully and are able to follow instructions.