Number the pages last, once nothing else will change. The numbers are stamped onto the page as content, not calculated live, so decide the position and the starting number before you commit.
The two things to get right are where they sit, allowing for binding and printer margins, and where numbering starts, if the document has front matter.
Numbering matters most on documents that will be printed, handled, referenced in a meeting, or filed alongside others. It is what lets someone say page fourteen and have everyone arrive at the same place, and it is what makes a dropped stack reassemblable.
Numbers are content, not a setting
A word processor keeps page numbers as a field that recalculates whenever the document changes. PDFs have no equivalent. Adding numbers means drawing text onto each page, exactly like adding a watermark or any other graphic.
That has two consequences. The numbers will not update if you later insert or remove pages, and they cannot be edited afterwards without editing page content. Both argue for numbering as the final step, once the document is settled. If a merge left pages out of sequence, fix the order of the merged PDF before any number goes on.
When numbering should not start at one
Most real documents do not want their first sheet labelled page one. A cover, a contents page and a blank are all sheets in the file and none of them is page one of the document.
This is what the starting number and page range options are for. You choose which physical page carries the first number and what that number should be, so the printed numbering matches the document's own structure rather than the file's.
- Cover, then bodyStart numbering at page 2
- Cover plus contentsStart at page 3
- Continuing another volumeStart value 47, not 1
- Appendices numbered apartNumber the ranges separately
- Everything numberedStart at page 1, value 1
When the pages already have numbers
Documents assembled from several sources often arrive already numbered, each part running from one. Stamping a new sequence on top produces pages carrying two different numbers, which is worse than either alone.
There is no clean way to remove printed numbers, because they are page content indistinguishable from any other text. The practical answers are to place the new number somewhere the old one is not, or to accept the existing numbering and add a separate identifier that is clearly different in position and style.
Where to put them
Position looks cosmetic and has real consequences once paper is involved.
The safe default
- Works for single and double-sided printing
- Never collides with a binding edge
- Easy to find when flicking through a stack
- Neutral on any page layout
For bound documents
- Visible when flicking a bound book
- Needs to alternate sides on double-sided pages
- Can collide with existing footers
- Must clear the printer's unprintable margin
Numbering for legal and archival use
Some contexts need more than a page count. Legal disclosure typically requires every page to carry a unique identifier that is stable across the whole production, often with a prefix identifying the party and a fixed number of digits.
The important property is uniqueness across the entire set rather than within one document, so that a single page can be identified unambiguously in correspondence months later. If that is the requirement, plan the scheme before numbering anything, because every letter and filing that cites a page number breaks when the production is renumbered. That scheme is Bates numbering, and PDFslime has a separate Bates numbering tool for the prefix and zero-padded digits.
Add page numbers in your browser
Choose the position, the starting number and the range. Nothing is uploaded.
Common questions
Getting the numbering right first time.
01Can I change the page numbers after adding them?
Not easily. Numbers are stamped onto the page as content, so changing them means editing page content. Add numbering as the final step, once the document's pages are settled.
02How do I start numbering after the cover page?
Set the numbering to begin at the physical page where the body starts, with a starting value of one. So if the body begins on sheet three, you number from position three with the first number being one.
03What if the pages already have numbers printed on them?
Existing numbers are ordinary page content and cannot be cleanly removed. Either place the new numbers where the old ones are not, or keep the existing numbering and add a clearly distinct identifier instead.
04Where should page numbers go?
Bottom centre suits almost any document. For a bound, double-sided book, use the outer corners and alternate them: odd pages on the right, even pages on the left. In PDFslime that is the Facing pages option, which switches corner by page parity for you.
05Will the numbers update if I add a page later?
No. They are drawn content rather than a live field, so inserting a page leaves everything after it mislabelled. If pages change, the numbering has to be redone from a clean copy.
06Do page numbers affect file size or quality?
Barely. Each number is a short line of text drawn with one of the standard PDF fonts (Helvetica, Times or Courier), which every reader already has, so no font file is embedded. Nothing else about the page is re-rendered or recompressed.