How to add a watermark to a PDF
A watermark is the simplest way to mark a document as a draft, label it confidential, or claim ownership of a file you're sharing. Slate stamps your text across every page without uploading the document.
Steps
- Open Watermark PDF.
- Drop in your file.
- Type your watermark text (for example, CONFIDENTIAL) and pick the opacity and angle.
- Download the watermarked PDF.
Tips
A diagonal watermark at low opacity is the hardest to crop out and the least distracting to read through. For numbered handouts, pair this with Add Page Numbers.
How a text watermark behaves
A watermark is drawn onto every page rather than shown only in your viewer, so it prints and displays for anyone who opens the file and cannot be switched off. You control its opacity and angle, which lets you keep the underlying text readable while still making a label such as DRAFT or CONFIDENTIAL unmistakable. Because it becomes part of the saved document, the mark travels with the file wherever it is shared.
Common problems and how to fix them
- The watermark hides the content: lower the opacity so the text underneath stays readable through it.
- It is too easy to crop away: place it diagonally across the middle of the page rather than in a corner.
- It did not appear on every page: apply it across the whole document, and add it after merging so later pages are covered too.
- It is too faint to notice: raise the opacity or shorten the wording so it reads clearly at a glance.
What to do next
Apply a watermark as the last step, after the document is fully assembled, so no page slips through uncovered. If you are still combining files, use Merge PDF first, then watermark the result. Many people add page numbers from Add Page Numbers at the same stage to give a report a finished, official look. As with every Slate tool, your file never leaves your device.