What this tool does
Page numbering sounds like a counter and is actually a set of conventions, most of which were settled centuries ago. Whether the cover is numbered, whether the count starts at one, whether the first section is in roman numerals and the body in arabic, whether the number goes at the foot or the head of the page, and whether it reads 7 or page 7 of 42 are all decisions, and getting them wrong is what makes a document look unprofessional rather than a student essay.
How it works
The number of pages has to be known before any of them can be numbered, because a page reading page 7 of 42 depends on 42. That means the whole document is counted first, and the total is then available to every page. It also means the number of pages can differ from the page you are looking at, since a start value or a skipped cover shifts the relationship between them, and the tool accounts for that rather than assuming the numbering equals the page index.
The available formats cover the conventions in real use. A bare number is the plain choice. A number with a total gives the reader their place in the document, which is what makes a printed document navigable when it is not bound. Roman numerals are the front-matter convention, where the introduction and contents are numbered but the body restarts at one, and letters restarting per chapter suit a loose-leaf reference. The start value is adjustable, so numbering can begin on the third page, which is the usual arrangement when a cover and a contents page are unnumbered.
Position is measured from the correct corner, which is not the top-left as it is in an image. A PDF's origin is the bottom-left with y increasing upward, so a number placed near the foot of the page is at a small y and one near the head is at the page height minus the margin. Getting this backwards is why some tools put page numbers in a corner nobody expects, and the position options here are named by where they appear to a reader rather than by coordinates.
Centring is measured rather than guessed. The three standard font families have different advance widths, and Courier is monospaced where Helvetica and Times are not, so a string that looks centred against one will not against another. The width of the actual string is therefore measured with the font before the position is resolved, which is why the number lands where you put it on every page rather than only on pages with the same digit count. This is the kind of detail that looks like nothing and is noticed immediately when it is wrong.
Worked example
A report needs numbering for a formal submission: a cover and contents page left blank, the introduction in roman numerals, and the body numbered from one with a total.
- Add the cover and contents to the exclusion list so they are not numbered
- Choose the roman numeral format and start at 1 for the introduction section
- For the body, switch to page X of Y so a reader can see the total
- Place the numbers at the bottom outside edge, and set the start value so the body begins at 1
A document numbered to the convention a formal submission expects, with the totals correct even on pages whose numbering does not match their position in the file.
Accuracy and limitations
- Page numbers are drawn text, not a PDF feature. They are as removable as any other drawing, and a document that needs tamper-proof numbering needs a cryptographic signature instead.
- The text is drawn using one of the fourteen standard fonts, so no font can be chosen and non-Latin scripts are limited. Numbers and Latin characters are unaffected.
- If the document is later re-sorted or pages are added, the numbering does not update, because it was drawn at the time you applied it.
- Existing stamps in the same position may collide with the new numbers, since neither tool knows about the other.
Frequently asked questions
- How do I add page numbers to a PDF?
- Choose a format, pick where the numbers should sit, and set a start value. The total is calculated automatically so a page can read page 7 of 42, and you can exclude a cover or contents page by listing the page numbers not to number.
- How do I skip numbering the cover page?
- Add the cover to the exclusion field using the page range syntax, so 1 for a single cover or 1-2 for a cover and contents page. Everything else is numbered and the total still reflects the whole document, including the excluded pages.
- Can I number pages as roman numerals?
- Yes, and the conventional use is front matter: the introduction and contents numbered in lower-case roman numerals, with the body restarting at one in arabic. Because the two sections are numbered differently you may need to run the tool twice, once per section, or use the start value to make the second run continue correctly.
- Why are the numbers not centred on my pages?
- Usually because the tool measured the string using one font and the reader rendered it with another, since the three standard font families have different widths and Courier is monospaced. This tool measures the actual string width with the font it draws in, so centring is exact and does not drift between pages with different digit counts.
- Are the page numbers part of the PDF, or just an overlay?
- They are drawn onto the pages as ordinary text, so they are as removable as any other content in the file. If you need numbering that cannot be altered, that is a digital signature feature rather than something a page-numbering tool can provide.
- Can I choose a font for the page numbers?
- Not a custom one. The numbering uses the standard fonts that every PDF reader already contains, which needs no embedding and keeps the file small. That is plenty for digits and Latin characters, and it is why a non-Latin script is not available here.