Add page numbers to a PDF

What this tool does

The tool writes a number on every page of a PDF, or on every page but the first. You choose the position, the text ("1", "Page 1", "1 of 12" or "Page 1 of 12"), the first number and the font size.

The numbers are added on top of the existing pages. Nothing else changes: text stays selectable, pictures are not compressed again, and bookmarks, links and form fields keep working.

How to use it

1. Choose a PDF, or drop it on the marked area, and wait until its number of pages is shown.
2. Choose the position: bottom or top, left, centre or right.
3. Choose the text. "1 of 12" and "Page 1 of 12" also show the last number.
4. Enter the first number and the font size in points. 1 and 11 are preselected.
5. Choose whether the first page gets a number. For a cover page, choose Leave it without a number.
6. Press Add page numbers and download the file. Its name ends in -numbered.

How the position is calculated

PDF measures in points of 1/72 inch. At the bottom, the baseline of the number is 36 points (half an inch, 12.7 mm) above the edge; at the top, its capitals end 36 points below the edge; on the left or right, the text starts or ends 36 points from the side. Half an inch is a common footer distance in word processors; it is a convention of this tool, not a rule of the PDF format.

The edges are those of the visible page: its crop box, the part of the page a reader shows (ISO 32000-1, section 14.11.2), where it lies within the page. So a scan with a trimmed border gets its number inside the trimmed area, not in the cut-off part.

A page that is stored turned (its /Rotate entry, section 7.7.3.3) is handled as it is shown. On a page turned by 90°, the bottom of what you see is the right edge of the stored page; the tool places the number there and turns the text by the same angle, so it reads the right way up like the other pages.

Numbers are counted from the first numbered page. With the first page left out and a first number of 1, page 2 gets 1. "Of 12" shows the last number written, which is the number of numbered pages when you start at 1. The text is set in Helvetica, a font every PDF reader has, in black.

Worked example

A licence agreement of 310 pages and 2,896,912 bytes should get "Page 1 of 309" at the bottom centre, without a number on its title page. In Chrome the tool numbered pages 2 to 310 as 1 to 309 in less than a second; the file became 2,739,375 bytes, smaller than before because pdf-lib stores the objects more compactly.

Page 2 is US Letter, 612 × 792 points. The text "Page 1 of 309" in Helvetica at 11 points is 68.06 points wide, so it starts at (612 − 68.06) ÷ 2 ≈ 272 points from the left edge, with its baseline 36 points above the bottom edge.

A test page of 400 × 600 points, stored turned by 90° and with a crop box that starts 20 points from the left and 40 from the bottom, got its number at the bottom right of the page as shown, inside the crop box, reading upright.

Common mistakes

• Numbering before merging. Merge the files first; otherwise every part starts again at 1.
• Numbering a document whose footer already has text or old numbers. The new number is drawn on top; choose a top position instead, or remove the old numbers in the original document.
• Choosing a large font size with "Page 1 of 309". The text gets wide; 9 to 12 points suit most documents.
• Using a password-protected PDF. It cannot be read; remove the protection first with a program that knows the password.