PDF Watermark Adder

What this tool does

The PDF Watermark Adder lets you stamp a text or image overlay onto every page of a PDF without uploading the file anywhere. For text watermarks you control the message, font size, colour, opacity, and rotation angle. For image watermarks you upload a PNG or JPEG, set a scale percentage, and choose an opacity level. Both modes offer a nine-cell position grid (three rows × three columns covering the corners, edges, and centre of each page) and a tiled mode that repeats the watermark across the entire page surface.

Why you might need it

Watermarks serve a range of legitimate purposes beyond simple branding. A law firm sending draft contracts to opposing counsel marks each version “DRAFT” so there is no confusion between interim and final documents. A design agency distributes low-resolution proofs with a “FOR REVIEW” overlay to prevent a client from treating the proof as the deliverable. A photographer sharing high-resolution sample images with a buyer applies a logo watermark so the images cannot be used without authorisation before payment. A teacher distributes a practice exam with “SAMPLE” overlaid so the file cannot be mistaken for the real assessment.

The image watermark mode is particularly useful for companies that want to embed their logo rather than a plain text label. Positioning the logo at the lower right corner with 20–25% opacity provides an unobtrusive but persistent branding mark that survives most screen captures and conversions.

How to use it

1. Drop your PDF onto the dropzone or click to browse.
2. Choose Text or Image from the watermark type selector.
3. For a text watermark: type the label, set font size, pick a colour, and adjust opacity (30% is a reasonable default). Change the rotation angle if you prefer something other than a diagonal.
4. For an image watermark: click Choose image, select a PNG or JPEG, then set a scale percentage (50% means the image is drawn at half its original pixel dimensions) and an opacity level.
5. Click a cell in the 9-cell position grid to choose where the watermark appears, or tick Tiled to repeat it across the whole page.
6. Click Apply watermark and wait for the processing indicator.
7. Download the result with Download PDF.

Common pitfalls

PDF pages vary in size. A single file might mix A4 portrait pages with a landscape summary sheet — the watermark position is computed relative to each page’s own dimensions, so “centre” always means the centre of whichever page is being drawn, regardless of its orientation. This is usually the desired behaviour, but it means that a tiled image watermark will have a denser or sparser grid depending on page dimensions.

Very large image files used as watermarks can increase the PDF size significantly, because pdf-lib embeds the full image once and references it from each page. If the output file is unexpectedly large, resize the source image before uploading it as a watermark — a logo rendered at 800 × 600 pixels is more than sufficient for any PDF page at typical reading resolutions.

Tips and alternatives

For professional-looking “CONFIDENTIAL” text watermarks, try a dark red colour (#cc0000 to #990000), 45° rotation, and opacity between 15% and 25%. For a subtle branding mark, use a light grey (#cccccc) at 40–50% opacity without any rotation, positioned at the bottom right. If you want a bolder statement, the PDF Stamp Adder offers a curated set of predefined stamps in standardised colours, which may be more appropriate for formal document workflows than a custom text watermark.