Add Page Numbers to PDF

How to Use

Upload a PDF, choose where you want the page numbers to appear, set a starting number (useful if this document continues from another), and a font size, then download. Every page gets a number in the position you chose, in plain black text. The whole process runs locally in your browser using the pdf-lib library, so the file is never sent to a server, there is nothing to wait on except your own device's processing speed.

Understanding the Six Position Options

The position grid gives you six anchor points: top-left, top-center, top-right, bottom-left, bottom-center, and bottom-right. Bottom-center is selected by default because it's the convention most readers expect from books, reports, and academic papers. Each option keeps a fixed 28-point margin from the nearest edge, which is roughly a third of an inch, enough space that the number never touches the edge of the printed page even after a printer's own unprintable margin is factored in.

The horizontal position matters more than it looks. For left and right anchors, the number sits flush against the margin regardless of how many digits it has. For center anchors, the tool measures the actual pixel width of the number at your chosen font size and centers it around the page's midpoint, so "1" and "100" both look centered even though "100" is roughly three times wider on the page.

Worked Example: Where the Number Actually Lands

Take a standard US Letter page, 612 points wide by 792 points tall (8.5 x 11 inches at 72 points per inch). At the default 12pt font size, the digit "1" measures about 6.67pt wide in Helvetica, while "12" measures about 13.34pt. With bottom-center selected, page 1's number is drawn at roughly x=302.7, y=28, which is dead-center horizontally and 28pt up from the bottom edge. If that same document has 12 pages and you switch to bottom-right, page 12's "12" is placed at roughly x=570.7, y=28, tucked into the corner with the same 28pt margin from both the right and bottom edges. Switching to top-left instead moves the anchor to x=28, y=754, since the vertical margin from the top also accounts for the text's own height so the digits don't get clipped by the page boundary.

This is why the position preview matters more than the raw coordinates: two PDFs with different page sizes (say, one Letter and one A4) will place numbers at different absolute coordinates even with identical settings, because the tool always measures each page's actual dimensions rather than assuming a fixed size.

Starting From a Number Other Than 1

The "Start From" field is for documents that are logically a continuation of something else, a chapter that begins at page 45 of a larger book, or an appendix that should pick up where the main report left off. If you set Start From to 5, the first page of the uploaded file is stamped "5", the second "6", and so on. For example, with bottom-center selected and Start From set to 5, the third physical page in the file (which displays the number "7") lands at the same x=302.7, y=28 coordinates as any other single or double-digit centered number, since the position logic only cares about the rendered text's width, not what the underlying page count is.

Choosing a Font Size

The font size field accepts anything from 6pt to 48pt. Anything under 9pt starts to look cramped and can be hard to read once a document is printed and photocopied a few times, which is common with legal filings and academic submissions. Most style guides for theses, manuscripts, and business reports land somewhere between 10pt and 12pt, the same range used for this tool's own default. Larger sizes (18pt and above) are occasionally used for cover pages or section dividers where the number itself is meant to be a visual anchor rather than a quiet footer detail.

Common Mistakes When Numbering PDFs

The most frequent issue is applying numbers to a document that already has numbers baked into the page content, for example a scanned book where the page number was part of the original printed page. Because this tool draws new text on top of the page rather than detecting and replacing existing numbers, you'll end up with two numbers unless you pick a position that doesn't overlap the original. Zooming into the preview page before downloading is the easiest way to catch this before it becomes a wasted export.

Another common mistake is numbering a document that mixes cover pages, table-of-contents pages, and content pages, expecting the numbering to skip the front matter. This tool numbers every page sequentially starting from your chosen number; if you want the cover page to stay unnumbered, split it out first with a page-splitting tool, number the remainder, then merge them back together.

Real-World Use Cases

Students assembling a dissertation or thesis often need sequential numbering that starts after an unnumbered title page and abstract. Legal and compliance teams number exhibits and filings so that pages can be referenced unambiguously in court or during an audit. Freelancers and consultants add page numbers to proposals and reports before sending a final PDF to a client, since a numbered document looks more finished and makes it easier for the recipient to reference a specific page in a follow-up email or call. HR departments do the same with employee handbooks and policy documents that get printed and distributed physically.

How This Works Under the Hood

The tool loads your PDF's raw bytes into pdf-lib, a JavaScript library that can parse and rewrite the PDF file format entirely client-side. It embeds the standard Helvetica font (a font baked into virtually every PDF reader, so no font file needs to be uploaded or bundled), then loops through every page, calculates the (x, y) coordinate for your chosen position, and calls a low-level "draw text" instruction directly onto that page's content stream. The modified document is then re-saved as a fresh set of bytes and offered to you as a downloadable file, all of it happening in memory in your browser tab, with nothing ever transmitted over the network.

Frequently Asked Questions

Can I start numbering from something other than 1?

Yes, the "Start From" field lets you begin at any number, useful when this PDF is a continuation of another document's page sequence.

Does this overwrite existing page numbers already in the document?

No, this adds new text on top of the page; if your document already has numbers printed in the content itself, both will appear. Choose a position that avoids overlapping any existing numbering.

Will the numbers land in the right spot on both Letter and A4 pages?

Yes. The tool reads each page's actual width and height from the PDF and recalculates the position for that page, so a US Letter page (612 x 792pt) and an A4 page (595 x 842pt) both get correctly placed numbers even if they're mixed in the same file.

Can I change the font or color of the page numbers?

Not from the interface. Numbers are stamped in Helvetica, in dark charcoal text, which stays legible against nearly any background. If you need a specific brand font or color, that requires desktop PDF editing software.

What happens if I upload a password-protected PDF?

The tool can't open it. It relies on pdf-lib to parse the file structure in your browser, and encrypted PDFs fail to load with an error. Remove the password with a PDF unlock tool first, then add page numbers.

Does adding page numbers compress or degrade the rest of the PDF?

No. The tool only draws new text objects on top of each existing page; it doesn't re-encode images, re-render text, or recompress anything already in the document. The output file size is typically within a few kilobytes of the original, just enough to store the new text objects and font reference.