Why a document needs numbers on it
Not for navigation. Nobody scrolls a PDF looking for page seventeen. Page numbers exist for the moment a document leaves the screen and becomes an object in the world.
Once it is printed, it can be dropped, restapled in the wrong order, or split across two folders. Once somebody is on a call about it, they need to be able to say "page four, third paragraph" and be understood. Once it is scanned back in by somebody else, the only way to know a page went missing is that the numbers skip.
That is why "of 20" is worth having. A page marked 7 tells you nothing when 8 has gone astray. A page marked "7 of 20" in a stack of 19 tells you immediately.
How this tool works
The number is measured and placed rather than positioned by guesswork: the width of the text at that size is worked out first, then the corner and margin you chose decide where it goes, so a right-aligned number sits the same distance from the edge whatever it says.
When you skip the cover, the total counts numbered pages rather than pages in the file, so the second page of a twenty-one page document reads "1 of 20" rather than "2 of 21". Getting that wrong is the classic fault in a numbering tool and it is only visible if you read it.
The cover sheet problem
Almost every document that needs numbering has a front page that should not carry one, and this is where most free tools quietly get it wrong.
They let you skip the first page, then number the second page "2 of 20", because they are still counting the cover. What you actually want is for page two to be "1 of 19": the cover is not part of the numbered document, so it should not be in the count either.
That is what happens here. Turn on leaving the first page bare and the total drops with it. The panel on the right shows the exact text for every page before anything is written, so you can check it rather than trust it.
Choosing where they go
Bottom centre is the conventional choice and it is conventional for a good reason: it is the one position that survives being printed double-sided, hole-punched, or bound down either edge.
Bottom right suits anything that will be flicked through in a folder, since that is the corner your thumb lands on. Top right works for a document that gets stapled and folded back.
Whatever you pick, check the corner is actually empty first. This adds numbers, it does not replace them, so a document that already has a footer from Word will end up with two.
Starting somewhere other than one
A document is often a section of something bigger: appendix C of a report, part two of a pack assembled from several sources, or a chapter that continues from a file somebody else produced.
Setting the start number lets the numbering carry on rather than restarting, so the whole assembly reads continuously when it is printed and bound together.
Where Bates numbering is the right tool instead
If you are preparing a bundle for a dispute, a claim or a legal matter, ordinary page numbering is not enough.
Bates numbering runs a single continuous sequence across every document in a set, usually with a prefix identifying the party or the batch, and produces a record of which number landed on which page of which original file. That record is the point: it is what lets two sides refer to the same page unambiguously months later.
This tool does the ordinary version well and does not pretend to do the other one.
Nothing added that you did not ask for
No account, no email address, no page limit, no watermark and nothing added that you did not ask for. Your document is opened, numbered and saved by your own browser.
That last one is not a throwaway. Free numbering tools are one of the commonest places a promotional footer appears on a document, and once it is flattened into a contract or a tender it stays there. The only marks this adds are the numbers you asked for.
Common questions
How do I add page numbers to a PDF without Acrobat?
Drop the file in, choose how the numbers should read and where they go, and download it. No account, no upload and no page limit. It shows you exactly what will be printed on each page before it writes anything.
Can I skip the cover sheet?
Yes, and the count adjusts with it. Skip the first page and page two becomes "1 of 19" rather than "2 of 20", which is the behaviour you want and the thing most tools get wrong.
Can I start at a number other than one?
Yes. Useful when a document is one section of something larger and the numbering has to carry on from the previous part.
Will this remove numbers the document already has?
No. It adds numbers on top of whatever is there. If your document came out of Word with its own footer, you will end up with two sets, so pick a corner that is empty. The preview will not catch this for you because it does not know what is already on the page.
What is the difference between this and Bates numbering?
Bates numbering is the legal version: a continuous sequence running across several merged documents, usually with a prefix, recorded so any page can be referred to unambiguously in correspondence or in court. This is ordinary page numbering for ordinary documents.
Is my file uploaded?
No. It is opened, numbered and saved by your own browser, so no request leaves the page. The consequences are the ones the upload sites cannot match: no page limit, no size cap beyond what your device holds, no queue when they are busy, and it works with the network off. Documents that need numbering tend to be contracts, tenders and operation and maintenance manuals, which are exactly the files worth keeping off somebody else’s server.