Add Watermark to PDF Online Free — Custom Text
Add CONFIDENTIAL, DRAFT or custom text watermarks to PDFs free. Choose position, opacity and color. No upload. Permanent watermark in seconds.
About Watermark
Watermark stamps one line of text, such as CONFIDENTIAL, DRAFT or a recipient's name, onto every page of a PDF. You choose diagonal, centre, top or bottom placement, the size, opacity, colour and, for diagonal placement, the angle. The text is written into each page's content rather than added as a comment.
How to use Watermark
- Drop in the PDF.
- Type the watermark text. Keep it short; long text at a large size runs off the page.
- Pick a position: Diagonal, Center, Top or Bottom. Top and bottom are horizontal bands near the page edge.
- Set font size (20 to 120), opacity (5% to 60%) and colour. For Diagonal, the rotation slider goes from -90° to 90°, starting at 45°.
- Check the preview card, then apply. The watermarked copy downloads as a new file and the original is left unchanged.
When it helps
Marking drafts
A light grey DRAFT across each page stops a work-in-progress contract or report being mistaken for the final version when it is forwarded around.
Tracing who leaked a copy
Watermark each recipient's copy with their name or organisation before sending, for example 'Copy for ABC Builders'. If a copy turns up somewhere it should not, you know which one it was.
ID copies submitted for one purpose
Before sending an Aadhaar or PAN copy, stamp it with the purpose and date, such as 'For SIM verification only 15/10/2026'. It makes reuse of the copy for something else harder to pass off.
Tips
- Opacity around 15% to 25% keeps the page readable on screen and in print; above 40% the watermark starts competing with the text.
- Grey or a muted colour reads as a watermark. Bright red at high opacity reads as damage to the document.
- If you need both a watermark and a password, add the watermark first and Protect last; the watermark tool does not decrypt files.
- Run a test on a two-page sample first if the document mixes portrait and landscape pages, then check both in the preview before doing the full file.
Limitations
- Latin text is written with the standard Helvetica Bold font as real text. Text in Tamil, Hindi, other Indian scripts, Arabic, Chinese and so on (or symbols outside Latin-1) is drawn by your browser with your device's fonts, so the letters join correctly, and is added as a sharp transparent image: it looks right but cannot be selected, searched or copied in the PDF.
- The watermark is centred on the page at any angle, but long text at a large size can still run past the edges of small pages. Reduce the size if it looks cut off.
- It is ordinary page content, not tamper-proofing. Someone with a full PDF editor can select and delete it. It also does not flatten the page, so text underneath remains selectable.
- Only one text line per run, the same on every page; there is no image or logo watermark, no tiling, and no page-range choice. Password-protected PDFs should be unlocked first.
What happens to your files
The PDF is opened and modified by pdf-lib in your browser, using a standard PDF font for Latin text and your device's own fonts for other scripts; no network request is made and the file is not uploaded. The watermarked result is stored in the on-device workspace (IndexedDB, files expire after seven days) and downloaded to your device.
Add CONFIDENTIAL or DRAFT Watermark in Seconds
Protect your documents with professional watermarks in under a minute. Type any text — CONFIDENTIAL, DRAFT, DO NOT COPY, or your company name — and File Studio stamps it across every page. Choose diagonal placement for maximum visibility or position the watermark at the top, bottom, or centre. The watermark is drawn on top of the existing page content, so keep the opacity low enough for the text underneath to stay readable.
Customize Position, Opacity, Color and Font Size
Every watermark parameter is adjustable. Set opacity to make the watermark subtle enough that underlying content remains fully readable, or increase it for prominent branding. Pick any colour with the colour picker and set the font size from 20 to 120 to suit the page size. These controls ensure your watermark looks professional regardless of whether the PDF contains dense text, images, or a mix of both.
Written Into the Page, Not Added as a Comment
File Studio writes the watermark directly into each page's content stream, rather than as an annotation that a viewer can hide or a reviewer can delete with one click. Latin text goes in as real text; Tamil, Hindi and other scripts are drawn with your device's fonts so the letters join correctly, and placed as a sharp image. Either way it is part of the page in every reader and in print. It is still ordinary page content, though: someone with a full PDF editor can select and delete it, so a watermark marks a document's status and discourages misuse rather than making removal impossible.
Frequently asked questions
- How do I add a watermark to a PDF for free?
- Upload your PDF, type your watermark text (e.g. CONFIDENTIAL or DRAFT), choose position and opacity, then click Apply. Your watermarked PDF downloads instantly.
- Can I add a diagonal watermark?
- Yes. Select 'Diagonal' placement. The text is rotated 45° by default and a slider lets you set any angle from -90° to 90°. Keep opacity low so the content underneath stays readable.
- Will the watermark be permanent?
- It is written into each page's content as ordinary text, not added as a comment or annotation, so a normal viewer cannot hide it. Someone with a full PDF editor can still select and delete page text, so treat it as a clear label and deterrent, not tamper-proofing.
- Are my files uploaded to a server?
- No. File Studio is built on a strict local-first architecture. Every PDF operation — merging, splitting, compressing, redacting — runs entirely inside your browser using JavaScript. Your files never leave your computer. You can even disconnect your internet after the page loads and the tools will continue working perfectly.
- Is File Studio completely free?
- Yes, 100% free with no limits. There are no file size caps, no daily limits, no watermarks added to your output, and no account or email required. All tools are free forever.
- Does it work on mobile and tablet?
- Yes. File Studio is fully responsive and works on Android and iOS browsers. All processing happens locally on your phone's or tablet's hardware.