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Add a Watermark to a PDF

Drop a PDF, type your text, stamp every page. Nothing leaves your browser.

This tool does not add a removable annotation or a floating layer — it draws your watermark text directly into each page's content stream, the same instruction list that draws the page's own text and graphics. The result is a rotated, semi-transparent run of text rendered at a fixed position on every page, permanently mixed into the page's drawing instructions. Unlike server-based watermarking tools, the PDF is never uploaded: the file is opened and rewritten with JavaScript (pdf-lib) locally, so your document never leaves your machine.

Drop a PDF here, or

One PDF, up to 64 MB. Stays in your browser — nothing is uploaded.

How to use

  1. Drop your PDF

    Drag a PDF (up to 64 MB) onto the dropzone or click to choose one. The tool reads it locally and shows the file name and page count.

  2. Type your watermark text

    Enter whatever wording you need — DRAFT, COPY, CONFIDENTIAL, a company name, a case number. There is no forced preset; the field starts with a suggestion you can replace entirely.

  3. Adjust opacity, color, and rotation

    Pick how faint or bold the stamp should be (0.1 for barely-there, 0.5 for bold), a color, a font size, and a rotation angle. The defaults (0.3 opacity, gray, 45°) mirror the classic diagonal “DRAFT” look.

  4. Stamp and download

    Click the button. The tool draws the text onto every page and offers a single download named after your original file with “-watermarked” appended.

Frequently asked questions

Is the watermark removable?
Not casually. Because the text is drawn into each page's content stream rather than attached as a separate annotation or layer, there is no “remove watermark” button in a PDF viewer that will strip it back out. Removing it requires editing the page's drawing instructions directly, which is far more involved than deleting an annotation.
Can I use my own text instead of a preset?
Yes — the watermark text field is a free-text input, not a locked dropdown. Type anything: DRAFT, COPY, a company name, a case or version number. There is no requirement to use CONFIDENTIAL; that's only a starting suggestion you can clear and replace.
Does this watermark every page, including a cover page?
Yes. The tool loops over every page in the document and stamps each one identically — there is currently no option to skip the first page or apply a different watermark to a subset of pages.
Can I make the watermark lighter or darker?
Yes. The opacity control ranges from 0.1 (very light, good for backgrounds you don't want to obscure text) to 0.5 (bold and hard to miss). You can also pick a color — gray, red, or blue — to further tune how much it stands out.
Does watermarking reduce PDF quality?
No. The original page content — text, images, vector graphics — is untouched; the watermark is an additional drawing operation layered on top using the embedded Helvetica Bold font. Nothing in the source is rasterized, recompressed, or re-rendered.
Can I add an image or logo watermark instead of text?
Not with this tool — it is text-only, drawing a string with pdf-lib's drawText. Stamping a logo or image watermark onto every page is a different operation (drawImage plus size/position math) and would need a separate tool.

About

How opacity, rotation, and centering work under the hood

pdf-lib's drawText accepts an opacity that sets the graphics state's fill alpha for that operation, so the text blends with whatever is beneath it instead of fully covering it. Rotation is applied around the text's baseline-start point using pdf-lib's degrees() helper, which pdf-lib translates into a PDF content-stream rotation matrix. To keep the rotated text visually centered on the page regardless of angle, this tool measures the string's width (font.widthOfTextAtSize) and height (font.heightAtSize), treats half of each as the offset from the baseline-start point to the text's visual center, and rotates that offset vector by the chosen angle to solve for the baseline-start coordinates that place the rotated center exactly at the page's midpoint — the same trigonometry used to rotate any point around a pivot.

A real scenario: flagging draft contracts before internal review

Picture a draft services contract or a financial statement that is still being reviewed internally and is not ready for anyone outside the team. Stamping a diagonal, semi-transparent “DRAFT” or “CONFIDENTIAL — INTERNAL REVIEW” across every page makes the document's status visually unmistakable the moment someone opens it, even if it later gets forwarded by accident or saved into the wrong shared folder. Because the watermark is burned into the page content rather than a toggleable layer, it survives being printed, screenshotted, or converted to an image — which is exactly the point for a document you want to be obviously unfinished wherever it ends up.

Sources & references

Authoritative references behind the math, constants, and tables on this page. Verified by Buğra Sözeri on the dates shown and re-checked at every deploy.