Adding page numbers to a PDF that doesn't have them — or that has them in the wrong position — requires either editing the source document before export or adding a header/footer to the existing PDF. Both approaches work; which to choose depends on whether you still have the source file.
The Source Document Approach: Always Cleaner
If you have the original Word document, Google Doc, or design file, add page numbers there before exporting. In Word: Insert → Page Number → choose the position (top or bottom, left, center, or right). In Google Docs: Insert → Page Numbers → select the layout. The page numbers become part of the document's header or footer and export cleanly to PDF as vector text that's sharp at any zoom and any print size.
This approach also makes it easy to customize: start numbering from a specific number (useful when the first few pages are a cover and table of contents that shouldn't count), use different numbering styles (Roman numerals for front matter, Arabic numerals for body content), or skip numbering on certain pages. All of this is straightforward in Word and most document editors, and much harder to do after the fact in a PDF.
Adding Page Numbers to an Existing PDF With Acrobat Pro
Adobe Acrobat Pro adds page numbers through the header and footer feature. Go to Tools → Edit PDF → Header & Footer → Add, and configure the number position (left, center, or right in the header or footer area), the starting number, the font and size, and which pages to apply it to. Acrobat applies the numbers consistently across all specified pages and embeds them as permanent content.
Acrobat also lets you define page ranges for the numbering — you can skip the first two pages (a cover and a table of contents) and start numbering from page 3 with the number displayed as "1." This mimics the source-level control that Word provides, which makes Acrobat's header/footer tool the right choice when you need precise numbering control and can't go back to the source.
Browser-Based Options
Several browser-based tools add page numbers to existing PDFs. WukongPDF's PDF Editor includes a page numbering feature where you specify position, starting number, font size, and page range, then download the numbered PDF. The result is a PDF with page numbers added as a text layer — not as editable header/footer fields, but as fixed content baked into the pages.
For a simple task like numbering all pages starting from 1 with the number centered at the bottom, browser tools get the job done quickly. For more complex requirements — different number formats on different sections, numbers that skip certain pages, or numbers in a specific typeface to match the document's design — Acrobat Pro or the source document approach gives more control.
Logical Page Numbers vs. Physical Page Numbers
PDFs have two numbering systems that can create confusion. Physical page numbers are the actual position in the file — the first page is physically page 1, the second is page 2, and so on. Logical page numbers are what's displayed in the viewer's page counter and in the page number printed on the document. These can be offset: a book with a 3-page preface might number those pages i, ii, iii, then start the body at page 1 — so what the viewer calls "physical page 4" is labeled as "page 1" in the document.
Acrobat Pro can set logical page numbers through the page thumbnail panel: right-click a page, choose Page Properties, and set the numbering style and start number. This affects what the viewer displays in its page counter and what Ctrl+G or the Go To Page dialog accepts as input. For long documents where the viewer's displayed page number should match the printed page number, aligning these two numbering systems makes navigation much less confusing.