A watermark does one job well: it tells everyone who looks at a page what that page is. DRAFT, CONFIDENTIAL, SAMPLE, "Prepared for Acme Ltd", or your logo in the corner of a portfolio. It's a label you can't miss and can't accidentally crop out of a printout.
What it doesn't do is lock anything. A determined person with the right software can usually take it off. So the useful question isn't "how do I make it impossible to remove" but "how do I make it obvious, readable and annoying enough to remove that nobody bothers". That's mostly a matter of a few settings.
Adding the watermark on EddiesPDF
Open Watermark and drop your PDF on the page. Everything happens in your browser, so the file isn't uploaded. You get a live preview of one page on the left and the settings on the right.
- Pick "Add text" or "Add image".
- For text, type into "Watermark text". It starts as CONFIDENTIAL in red, 60 pt, Helvetica. Change the "Font", "Font size" and "Color" to taste.
- For an image, click "Choose image" and set the width with the slider (it's a percentage of the page width; the height follows).
- Under "Location on page", choose "Center", "Diagonal", one of the four corners, "Custom" or "Tile across the page".
- Set "Opacity" and "Rotation".
- Leave "Pages" on "All pages", or pick "Specific pages" and type something like 2,3,10-20.
- Click "Add watermark" and download the result.
The preview is the real output for that page, not a mock-up, so it's worth flicking to a page with dense text or a photo using the "Preview page" box before you commit. With "Custom" selected you can also click on the preview to put the watermark exactly where you clicked.
PNG and JPG images go into the PDF unchanged. Other image formats are converted to PNG first. If your logo has a transparent background, use a PNG, because a JPG will bring a white rectangle along with it.
Opacity, rotation and why 30% is the default
Opacity runs from 0% (invisible) to 100% (solid). The tool starts at 30%, which on most text documents leaves the words underneath easy to read while the mark is still obvious from across a room. For a pale "SAMPLE" across a brochure, 15-20% is usually plenty. For something that must not be mistaken for a final version, I'd go to 40% or more and accept that the page gets busier.
Rotation is in degrees clockwise. 315° is the classic diagonal running from bottom left to top right, and it's what "Diagonal" sets for you. The default "Center" position also starts at 315°, so if you want a flat, horizontal stamp in the middle, set rotation to 0. Picking a corner resets rotation to 0, since a tilted word in a corner tends to run off the page.
Tiling, and why it's harder to get rid of
A single diagonal word in the middle of the page is easy to work around: crop, screenshot the top half, or paint over one area. "Tile across the page" repeats the mark in a grid that covers the whole page. When you switch to it, the tool shrinks the text to 36 pt (or the image to 20% width) so several copies fit.
You can adjust "Horizontal gap" and "Vertical gap" (in points; 72 pt is an inch) and turn "Offset alternate rows" on or off. With the offset on, every second row shifts half a step like brickwork, which leaves fewer clean gaps for someone to crop out. It also looks less like wallpaper.
Tiled watermarks are the right choice for things like ID scans you're sending to a landlord ("For tenancy application only, 2026"), because the text crosses every part of the document, including the photo.
Over the content or behind it
Under "More options" there's a "Layer" setting: "Over the content" (the default) or "Behind the content".
Over is drawn on top of everything. It's always visible, but it sits on the text, which is why opacity matters.
Behind is drawn first, so text and images are painted over it and stay fully crisp. It looks cleaner on documents exported from Word or a design app. The catch: a scanned page is one big image that covers the entire page, so a watermark placed behind it is completely hidden. The same goes for pages with a solid coloured background. If the preview shows nothing after switching to Behind, that's why.
One file per recipient
A small feature that's easy to miss: each line you type in "Watermark text" produces a separate PDF. Type five names on five lines and you get five copies, each with its own name on every page, downloaded together as a ZIP.
This is the practical way to deal with leaks. If a document gets passed on and every copy carries the recipient's name, the copy that shows up tells you where it came from. It doesn't prevent anything, but it does change how people behave once they know about it.
How easy is it to remove a watermark
Honestly, easier than most people assume. The watermark is drawn into the page content itself, so it isn't a comment or annotation that someone can click and delete in Preview or Adobe Acrobat Reader. But:
- A text watermark is real text. Anyone who copies text from the page will often get the word CONFIDENTIAL in the middle of what they pasted, and the rest of the page text is still there to copy.
- Editors that can change page content (Acrobat Pro and similar) can select the watermark and delete it.
- Anyone can take a screenshot, crop around a single mark, or retype the content.
If you want it to stick, the strongest option here is to watermark first and then run the file through Flatten PDF with "Flatten everything". That turns each page into an image, so the watermark and the content become the same pixels. The trade-off is real: text is no longer selectable or searchable, and the file usually gets bigger. Protect PDF can also restrict modifying and copying, though some readers ignore permission settings, so treat that as a speed bump rather than a lock. The guide to password protecting a PDF explains what those permissions actually do.
For anything that has to be genuinely hidden, a watermark is the wrong tool. Remove the content instead; see how to redact a PDF properly.
Save your settings before you forget them
If you watermark the same kind of document every week, click "Templates", give the current settings a name and click "Save current". Next time, "Use" loads the text, style, position and pages back in. Templates are stored in this browser only, and images over 1 MB aren't saved with them, so a large logo has to be chosen again. And before you send anything, flick the preview through a few different pages. A mark that sits nicely on a page of text can land right on top of a signature or a table total two pages later.
Also useful: Flatten PDF · Protect PDF
