How to add page numbers to a PDF
Easy if you still have the original Word file; much harder if all you have is the finished PDF. Here is what actually works.
The easy case: you still have the original document
If the PDF came from Word or Google Docs, the simplest path is to add page numbers in the original document (Word: Insert, Page Number; Google Docs: Insert, Page numbers) and re-export to PDF. This gives full control over the numbering format and skips touching the PDF at all.
When you only have the PDF
Often the original document is gone, came from someone else, or is a scan, and page numbers need to be stamped directly onto the existing PDF. This is a different job: adding a small text layer to each page rather than reflowing a document, and it is something neither Preview on a Mac nor the built-in PDF viewers on Windows, iPhone or Android can do.
On a Mac, Windows, iPhone or Android
None of the built-in PDF viewers on any of these platforms, including Preview, Edge's reader, and the Files apps on iPhone and Android, offer a way to stamp page numbers onto an existing PDF. This is a genuine gap across every platform, not something hidden in a menu.
A dedicated tool for stamping numbers onto a PDF
Stayput's add page numbers tool stamps a number onto every page directly, with a choice of position (corner or centre), format (plain number, or "Page 1 of 10"), font and starting number, done in the browser without uploading the document. It works the same way whether the PDF came from Word, a scanner, or somewhere else entirely.
Questions
Can I add page numbers to a PDF without the original document?
Yes, a tool that stamps numbers directly onto the existing PDF pages works regardless of what created the file, unlike adding numbers in Word or Docs which requires the original source document.
Can I start numbering from a page other than 1?
A dedicated PDF page-numbering tool typically lets you set a starting number, which is useful when a cover page or table of contents should not be counted.
Does adding page numbers change the PDF's existing content?
No, it adds a small text layer to each page without altering the original text or images underneath.
Can I number a scanned PDF the same way?
Yes, stamping numbers works on any PDF, including a scan with no underlying text layer, since it is adding a new number on top rather than depending on what is already there.