To add a watermark to a PDF for free, open Kopitiam's Add watermark tool, drop in your file, type your text (DRAFT, CONFIDENTIAL or your company name), pick a style and download. The watermark is stamped on every page, and the whole job happens in your browser. Your file is never uploaded.

A watermark is a label, not a lock. It tells everyone who sees the page what the document is and where it came from, but the text underneath stays readable, selectable and copyable. Read the section on what a watermark does and does not protect before you rely on one for anything sensitive.

Step by step

  1. Open the Add watermark tool and drop your PDF on the page, or click to choose a file.
  2. In Watermark text, type what you want stamped. The box starts with CONFIDENTIAL and takes up to 60 characters.
  3. Under Style, pick Diagonal, Tiled, Center or Footer.
  4. Drag the Opacity and Size sliders, and pick a Color: Red, Grey, Jade or Blue.
  5. Check the live preview of page 1. It updates as you change each setting.
  6. Click Download watermarked PDF. You get a copy named after your file with -watermarked on the end. Your original is not changed.

If you clear the text box, the download button is disabled and the tool asks you to type something. It never stamps words you didn't type.

Choosing the words

Pick the word that tells the reader what to do with the document. A few that work well:

  • DRAFT: a proposal, a contract under negotiation or a report still being reviewed. It stops an early version being mistaken for the final one.
  • CONFIDENTIAL: payslips, a tenancy agreement you are sharing with a lawyer, an internal price list. It reminds the reader the file should not travel further.
  • COPY or SAMPLE: a certificate, an invoice template or a design proof you are showing but not handing over for use.
  • Your company name: brochures, quotes and proposals, so the source stays visible if the file is forwarded.
  • Who it is for and why: "Copy for Maybank loan application only" on a passport scan or IC copy. This is one of the most useful watermarks you can add, covered below.

Text in other scripts works too. Chinese, Japanese, Korean, Greek and Cyrillic are stamped as real text. Arabic, Hindi and Thai are drawn as an image so the letters join and order correctly, which means that part of the watermark can't be selected or searched. It looks the same either way.

The four layouts, and when to use each

  • Diagonal: one line across the middle of the page at 45 degrees. The classic DRAFT look. Clear on every page without covering much.
  • Tiled: the text repeated across the whole page at 45 degrees. Harder to crop out of a screenshot, so it suits ID scans and anything you worry about being reused.
  • Center: one straight horizontal line in the middle. Good for SAMPLE or COPY on certificates and forms.
  • Footer: a small line at the bottom of each page. Best for a company name or "Internal use only" where you don't want to get in the way of the content. Footer text is capped at 18pt however large you set Size.

Diagonal and Center are centred on the page but are not shrunk to fit. A long phrase at a large size can run off both edges. If the preview cuts your words off, lower Size until the whole line shows, or switch to Tiled or Footer for long text.

Getting the opacity and size right

Opacity goes from 5% to 100% and starts at 25%. Size goes from 12pt to 120pt and starts at 48pt. The defaults suit a Diagonal stamp on an A4 page.

  • For text documents you still need to read, stay around 15% to 30%. The words underneath stay easy to read.
  • For Tiled, go lighter and smaller than you think. Many copies at 25% darken the whole page. Try 10% to 15% at 24pt to 36pt.
  • For a DRAFT you want nobody to miss, 30% to 40% in Red works.
  • For a Footer, opacity can go much higher, 60% to 100%, because it sits in the margin.
  • Grey is the quietest colour. Red reads as a warning. Jade and Blue suit a brand name.
Print a test page before you print 50. A watermark that looks faint on a bright screen can come out darker on paper, especially on a laser printer.

What a watermark does and does not protect

Kopitiam draws the watermark as text on top of each page. Nothing underneath is hidden, removed or locked. That is the honest picture for most watermarks, whichever tool made them.

A watermark does help in these ways:

  • It labels the document's status, so a DRAFT isn't signed or filed as final.
  • It discourages casual reuse. Most people won't bother to remove it.
  • It leaves a trail. A scan stamped "For ABC Property rental only, 10 Nov 2026" is far less useful to anyone who wants to misuse it somewhere else.
  • It shows where a document came from when it is forwarded around.

A watermark does not do any of these:

  • Hide information. The text under it can still be read, selected and copied. If the reader must not see something, use Redact instead.
  • Stop editing. Someone with a PDF editor can select the watermark text and delete it, because it is a separate object on the page.
  • Stop copying or printing. It doesn't add a password or permissions.
  • Prove a document is genuine. Anyone can type CONFIDENTIAL on anything.
Never use a watermark to cover an IC number, an account number or a salary. It sits on top of the text, which is still there. Redact the detail first, then watermark the copy.

If you want the watermark harder to remove, turn the pages into pictures after stamping. Run the watermarked file through PDF to JPG, then put the images back together with JPG to PDF. The watermark becomes part of each page image, so it can't be selected and deleted. The trade-off is that the text is no longer selectable or searchable either, and the file may get bigger. It is still not impossible to remove, just much more work.

When it goes wrong

  • "This PDF is password-protected": Kopitiam can't open locked PDFs yet. Open the file with its password in your PDF reader, use Print, then Save as PDF to make an unlocked copy, and watermark that copy.
  • "This PDF has editing restrictions": the file's creator blocked changes. The same Print, then Save as PDF step makes a copy you can watermark.
  • The watermark runs off the page: lower Size, or use Tiled or Footer.
  • The page looks too dark: lower Opacity, or use Grey.
  • The preview is slow on a big file: every change re-stamps the whole document so the preview is exact. On a long scan, give it a moment after each slider move.

Edge cases worth knowing

  • Scanned PDFs: the watermark sits on top of the scanned image, so it shows up on scans exactly as it does on typed documents.
  • Rotated and mixed page sizes: the watermark is placed on each page as you see it, so a landscape table in a portrait report gets an upright, centred stamp too.
  • Every page or none: the tool stamps every page. To watermark only some pages, split them out, watermark that part and merge it back.
  • Forms: the fields are kept. Filled-in field values are drawn above the page, so they can sit on top of the watermark.
  • Digitally signed PDFs: adding anything to a signed file means the signature will no longer validate. Watermark before signing, not after.
  • Very large files: there is no file-size limit in the tool. The real limit is your device's memory, so a phone may struggle with a 200-page scan that a laptop handles easily.
  • Text only: the tool stamps text. It can't place a logo image.

Is it private?

Yes. The watermark is added in your browser, and your PDF never leaves your device. That matters for the documents people watermark most: payslips, contracts and ID scans. There is no account to make, no sign-up, and Kopitiam doesn't add a watermark of its own to your download.