Use PDF for final documents
PDF is usually the safest format for resumes, cover letters, certificates, and forms because it keeps layout stable across job portals and recruiter devices.
Use image formats carefully
If a job application asks for an image, JPG is usually safest for photos and PNG is better for screenshots or graphics. If the portal asks for a document, convert images to PDF instead.
Final application check
Open every converted file before uploading. Check your name, contact details, links, page count, file size, and whether the portal preview matches the file you intended to submit.