What does the Add a PDF Watermark and Page Numbers do?
Use this tool when you need a browser utility that places a diagonal text watermark and optional page labels over every PDF page. It accepts one unencrypted PDF, optional watermark text, size and opacity settings, and a page-number choice and returns a downloadable PDF whose existing pages include the selected overlays. Results are deterministic for the same input except where cryptographic randomness, current time, or a live provider response is part of the task.
A visible watermark is not secure redaction
Use this tool to label drafts, review copies, or ownership visibly. Do not use it to hide confidential content: the original page objects remain in the PDF, and a determined editor may be able to remove an overlay.
How do you use it?
- Open one unencrypted PDF no larger than the 100 MB browser limit.
- Enter up to 60 watermark characters, choose a size and opacity, and enable or disable Page N of total labels.
- Select Process, review the page count and output size, then download watermarked.pdf.
Worked example
Mark a twelve-page review copy
Input
Source: draft.pdf (12 pages)
Watermark: INTERNAL REVIEW
Size: 48
Opacity: 0.20
Page numbering: enabledOutput
watermarked.pdf
Diagonal watermark on every page
Bottom labels: Page 1 of 12 … Page 12 of 12Text is rendered to a transparent image in the browser, which permits Unicode characters supported by the local system fonts before the image is embedded into each page.
Common errors and fixes
| Symptom | Likely cause | Fix |
|---|---|---|
| The PDF cannot be processed. | It is encrypted, damaged, incomplete, or not actually a PDF document. | Use an authorized unlocked copy or export a valid PDF before adding overlays. |
| The watermark is hard to read or covers important content. | Its size or opacity is inappropriate for the page design. | Reduce opacity for dense documents or adjust the size and process the original again. |
Important behavior of PDF Watermark
The watermark is an ordinary visible PDF overlay, not tamper-proof rights management or secure redaction.
Standards and implementation references
- pdf-lib documentation (opens in a new tab)Documents the browser-side PDF loading, PNG embedding, opacity, rotation, and save operations used by this workflow.
- MDN — HTMLCanvasElement.toBlob() (opens in a new tab)Documents the local transparent PNG generation step used for Unicode overlay text.
Frequently asked questions about PDF Watermark
Does the PDF Watermark upload my input?
No. Processing runs in the current browser tab, and the page does not send tool input to a KitLumi processing endpoint.
What input does the PDF Watermark accept?
It accepts one unencrypted PDF, optional watermark text, size and opacity settings, and a page-number choice. The workspace checks the input and reports malformed or unsupported values before it produces a result.
What does the PDF Watermark produce?
It produces a downloadable PDF whose existing pages include the selected overlays. Copy and download controls appear when the output format supports them.
What limitation should I know?
The watermark is an ordinary visible PDF overlay, not tamper-proof rights management or secure redaction.
What changed?
Added Unicode watermark text, Adjustable size and opacity, Page N of total labels, Local PDF export, responsive controls, explicit runtime disclosure, and task-specific examples and limitations.