Marking a Document Without Sending It Away
A watermark says what a document is: a draft that should not be quoted, a copy that is not the original, something confidential that was shared with one named person. It is a label applied to the page itself, which is why it keeps working after the file has been printed, forwarded and printed again.
The awkward part is that the documents most worth marking are the ones you least want to upload to a stranger. Here the mark is drawn in the page you are reading, so the tool is usable for the contracts and reports that are the actual reason for watermarking anything.
How to Watermark a PDF
The preview box updates as you adjust the settings, so you can judge the balance before committing.
- Load the document you want to mark. All pages start selected, since a watermark usually applies to the whole document.
- Type your text, or click one of the presets, CONFIDENTIAL, DRAFT, COPY, DO NOT COPY or SAMPLE.
- Choose the layout: one mark across the page, or tiled to repeat it in a grid.
- Set the size, angle and colour. Around 45 degrees is the conventional diagonal, and grey reads as a watermark rather than as content.
- Adjust the opacity until the mark is obvious but the text underneath is still readable, the preview makes this easy to judge.
- Deselect any pages that should stay clean, then press Add watermark and download the result.
Getting the Balance Right
A watermark has to be readable without making the page unreadable, and opacity is the setting that decides it. Around 15 to 20 per cent at a large size and a diagonal angle is the usual compromise: obvious enough to register at a glance, faint enough to read straight through. Below 10 per cent it disappears on a printed copy; above 40 per cent it starts to compete with the text.
Colour matters as much as opacity. A mid grey sits behind text of any colour without fighting it, which is why it is the default here. Strong reds and blues can look striking on screen and then swamp the page in print, especially on a laser printer that renders light colours darker than the screen suggests. If in doubt, print one page before running the whole document.
Settings for Common Purposes
Starting points rather than rules, adjust from here once you see the preview.
| Purpose | Text | Layout | Opacity | Angle |
|---|---|---|---|---|
| Marking a working draft | DRAFT | One across the page | 15–20% | 45° |
| Restricting circulation | CONFIDENTIAL | One across the page | 15–20% | 45° |
| Discouraging reuse of a sample | SAMPLE | Tiled | 10–15% | 30–45° |
| Identifying a recipient | A name or reference | Tiled | 8–12% | 45° |
| A subtle notice | Company name | One across the page | 8–10% | 0° |
Tiling repeats the text in a grid, which is harder to crop out of a screenshot than a single mark and more visible when only part of a page is shared. It also adds more ink to every page, so keep the opacity lower than you would for a single mark.
What a Watermark Does Not Do
The mark is drawn over the page content rather than beneath it. That is deliberate: a watermark placed behind a full-page scan would be completely invisible, which is precisely the case where it matters most. Because it becomes part of the page content, no reader can switch it off.
Equally, it is not encryption. Anyone with a PDF editor can work at removing it, and it places no restriction on copying, printing or extracting text. Treat it as a label rather than a lock. If the document genuinely must not be read by the wrong person, a watermark is the wrong tool, password protection or simply not sending the file are the real answers.
The Documents You Would Never Upload
There is a circularity in using an online watermarking service: you upload a confidential document to a third party in order to mark it confidential. Whatever the service promises about deletion, the file has been transmitted, processed and stored somewhere outside your control, which is the situation the watermark exists to discourage.
This tool never sends the file anywhere. The document is read into your browser, the text is drawn onto the selected pages with fonts already built into the PDF format, and the result is written back locally. It works offline, leaves no server-side copy, and requires no account.