Let the application instructions decide first
Before choosing a format, read the posting and the upload page for any stated requirement. Some employer systems accept only certain file types, and a few ask you to paste your resume text into a field instead of attaching a file. Following that instruction matters more than any general preference.
When the employer says nothing, Word and PDF are the two dependable defaults because most readers can open them. Avoid image-based files such as scanned pages or graphics exported from design software; those may look fine to a person but cannot be read as text by many application systems.
Understand what each format does well
A PDF keeps the layout fixed, so the document you reviewed is the document the reader opens, and it is difficult for someone else to edit by accident. A Word document is easy for an applicant tracking system to scan and for a recruiter or staffing agency to reformat, which is why some employers ask for it specifically.
Plain text is occasionally requested by older systems, and HTML or other web formats are best reserved for a personal site rather than an attachment. Choose the format the instructions name; if there are none, a PDF built from your own file is a reasonable default, with Word as the fallback when the employer prefers it.
Name the file and check the upload
Put your name in the file name so a reviewer sorting many attachments can identify it, for example “JordanLee-Resume.pdf.” Version numbers, internal codes, and words like “final” add nothing for the reader and can suggest the file is one of many drafts.
Export the PDF from the document you edited rather than printing it to a new file, then open the uploaded version once before you finish. The common mistake is a clean original paired with a submission that lost italics, columns, or bullet spacing during conversion.
Sources consulted
This guide is an original synthesis of the following career guidance. Read the source material for its full context.