How it works
The PDF is read by pdf-lib in this tab. For every page you chose, the tool writes one line of text in Helvetica, one of the 14 fonts every PDF reader has built in, so nothing needs to be embedded and the file grows by only a few kilobytes. The existing page content is left exactly as it was; the number is added on top. The preview is the real result for one page, drawn by Mozilla's pdf.js, so what you see there is what prints.
Where the number lands
PDF pages are measured in points, 72 to the inch, from the bottom-left corner of the page as it is shown. Left and right positions sit at the chosen distance from the side edge, and center positions are centered on the page width. A number at the bottom has its lowest letter tails resting on the margin line; a number at the top has its capital letters touching the margin line, so both sit the same visual distance from the edge.
Centered x = (page width − text width) ÷ 2
Bottom baseline = margin + 0.22 × text size
Top baseline = page height − margin − 0.72 × text size
The 0.22 and 0.72 are Helvetica's descender depth and capital height as a share of the font size, from Adobe's published font metrics.
Worked example. On a US Letter page (612 × 792 points), "Page 3 of 12" at 11 pt is 61.9 points wide. Bottom center with a ½ inch (36 point) margin puts it at x = (612 − 61.9) ÷ 2 = 275 points from the left, with its baseline 36 + 0.22 × 11 = 38.4 points up from the bottom edge.
Starting number and page range together
The count always goes up by one for each page that gets a number, starting from your starting number, and skips pages outside the range without using up a number.
| You want | Pages to number | Starting number | Result on a 10-page file |
|---|---|---|---|
| Every page numbered | (blank) | 1 | Pages 1 to 10 show 1 to 10 |
| Cover left blank, count starts after it | 2- | 1 | Page 1 blank, pages 2 to 10 show 1 to 9 |
| Cover blank but counted | 2- | 2 | Page 1 blank, pages 2 to 10 show 2 to 10 |
| Chapter 2 continuing from page 40 | (blank) | 41 | Pages show 41 to 50 |
| Only the appendix | 8-10 | 1 | Pages 8, 9 and 10 show 1, 2 and 3 |
Your file stays on your device
The page loads its code once, then opens, numbers and saves the PDF entirely inside this browser tab. There is no upload, no account, and no copy kept anywhere else, which matters for the things people usually number: court filings, theses, contracts and medical records. You can check by loading the page, turning off Wi-Fi, and numbering a file.
Questions people ask
How do I leave the cover page without a number?
Type 2- in "Pages to number". Page 1 is left blank and numbering starts on page 2. With the starting number at 1, page 2 shows "1", which is how most reports and theses count. If you want page 2 to show "2" instead, as if the cover had been counted, set the starting number to 2.
What does N count in "Page 1 of N"?
N is the last number printed, not the number of pages in the file. A 10-page file with the cover left blank and numbering from 1 reads "Page 1 of 9" through "Page 9 of 9". If you start at 41 to continue a series, the last page reads "Page 50 of 50" on a 10-page file, so for a continued series a plain number or "Page 1" is usually the better format.
Will the numbers cover text that is already on the page?
They can. Numbers are drawn on top of the page at the position and margin you choose, and the tool does not look for existing footers. If your document already has text in that corner, check the preview, then move the number to another position or increase the margin from the edge.
What happens with landscape, rotated or mixed-size pages?
Each page is measured on its own, as it appears on screen. A landscape page gets its number at the bottom of the landscape view, and a page stored with a 90 degree rotation is handled the same way, so the number reads the right way up. Letter, Legal and A4 pages in one file each get the number placed by their own width.
Can I number a password-protected PDF?
Yes, if you know the password. Type it when asked and the file is decrypted in this tab. The numbered copy you download has no password, because the tool cannot put the same protection back on. Protect the new file again if it needs a password.
Can I use Roman numerals, a prefix or Bates numbers?
Not yet. The four formats are 1, Page 1, Page 1 of N and 1/N, set in Helvetica at the size you choose. You can continue a Bates-style sequence by setting the starting number, but there is no text prefix or zero padding such as ABC000123.