How to add page numbers to a PDF

Nobody thinks about page numbers until they are missing. Then someone says "look at page seven" and everyone starts counting.

Adding them to a document you are still writing is easy, since every word processor does it. Adding them to a PDF that already exists is a different job, and it comes up all the time: a report put together from several sources, a scanned bundle, a contract with appendices from three different people.

What happens when you number a PDF

A PDF has no idea it has pages in the sense of numbered pages. It has a list of pages, in order, and that is all. There is no header, no footer and no field that updates.

So numbering a finished PDF means drawing the number onto each page: placing text at a set position, in a set font, on top of what is already there. Nothing else is touched. The existing content, text and images all stay exactly as they were, with a small piece of new text added on top.

Two things follow from that. The numbers are permanent once the file is saved, and they are drawn *over* the page, so a number placed where there is already content will sit on top of it.

The four decisions

Where. Bottom centre is the safe default and the most common in print. Bottom right suits documents that will be flicked through, because the eye lands on the outer corner. Top corners work for reference material where someone is looking things up.

What it says. The number on its own is right for most documents. "Page 3" adds nothing but is common in reports. "Page 3 of 12" is useful for anything printed or emailed, because it tells the reader whether they have the whole thing. That helps when documents get forwarded and pages go missing.

Where the numbering starts. There are two separate questions here, and people often mix them up:

• Which physical page gets the first number (the cover usually should not).
• What that number is (often 1, sometimes 47 because the document continues from another volume).

Whether it is printed double-sided. If so, an outer-corner number has to swap sides on alternate pages, or every second number lands in the binding.

The cover page problem

A report with a title page almost never wants "1" on the cover. It wants the cover clean and page 2 to be page 1.

That is one switch, and it does the counting for you: page one is skipped, and the page after it starts at 1 rather than 2. It sounds obvious, but if the count starts at page 2 without that switch, the first numbered page says 2.

A related detail is what "of N" means when a cover is skipped. On a 12-page document with an unnumbered cover, the correct total is 11, the number of pages that get a number, and not 12. A reader looking at "Page 11 of 11" should be looking at the last page.

Starting at a number other than 1

This comes up more than you would think:

• A chapter that continues from a previous file.
• A document whose front matter was numbered separately in roman numerals.
• A bundle where the first section was already numbered by someone else.
• Legal exhibits that continue a run.

Being able to say "start at 47" saves reassembling the whole document to get the numbering right.

Facing pages

For anything printed double-sided and bound, this matters. On a right-hand page the outer edge is the right; on a left-hand page it is the left. A number fixed to the right lands in the gutter on every second page, half-swallowed by the binding.

Switching on facing pages mirrors left and right placements on alternate pages so the number is always on the outer edge. Centre placements are unaffected, which is one reason bottom-centre is the low-risk choice.

Numbers over dark backgrounds

If your pages have a coloured footer, a photograph or a dark banner, a dark number placed there disappears.

Two fixes: change the number's colour, or put a small white pill behind it. The pill is more reliable because it works regardless of what is underneath, though it is visible as a shape. On a document with a consistent design, changing the colour is tidier.

Rotated pages

A PDF page can be marked as rotated. This is very common in scanned bundles where some pages went through the feeder sideways. If a tool ignores that, the number ends up along the side of the page as the reader sees it, turned 90 degrees.

The number should be placed on the page as it is shown, so a rotated page gets its number in the bottom corner *as you see it*. Check the output if your document mixes portrait and landscape pages.

Preview before you commit

Nine positions, several formats, a colour and a size is a lot to choose without seeing it. Page Numbers shows a live page beside the settings that updates as you change them, including the facing-page spread, so you can see where the number lands before you download.

Order first, numbers second

One practical warning. If you are assembling a document from several files, merge them and get the order right before numbering. Numbers are drawn onto pages permanently, so if you reorder afterwards, the numbers end up in the wrong sequence. Removing them means going back to the originals.

Assemble, check the order, then number. In that sequence it takes two minutes.

One last check before you commit

Numbers are drawn onto the page permanently, so spend thirty seconds on the preview.

Look at the busiest page in the document, such as the one with a table running to the bottom or a full-page image. That is where a number can land on top of content instead of in clear space, so it is the page that shows whether your position works.