Add Watermark to PDF - Text or Image Online Free

A PDF watermark tool stamps semi-transparent text or an image across each page to signal draft status, confidentiality, or brand ownership. Unlike printing a giant word on paper before scanning, a digital watermark layers on top of existing vectors and images without re-rasterizing them. This page uses pdf-lib drawText for text stamps and embedPng plus drawImage for logo overlays. The watermark sits in the page content stream above body text but below nothing - recipients see it in every viewer that honors standard PDF drawing operators.

Watermarks are a communication device, not encryption. Anyone with Acrobat can sometimes remove a simple overlay by editing the content stream, so treat text watermarks as deterrence for casual sharing - not DRM. For sensitive data, combine watermarking with access controls, password protection, organizational policy, and legal agreements. This tool makes honest drafts easy: stamp CONFIDENTIAL at 30% opacity on an investor deck before emailing partners, or place a low-opacity logo on photography portfolio PDFs so forwarded copies still show your brand.

Watermarking differs from headers, page numbers, and compression. Headers and footers repeat small text in margins; watermarks typically span the page center at an angle. Compression re-encodes images to shrink file size - it does not add visible stamps. If you need running folios, use PDF page numbers or PDF headers & footers alongside or instead of a diagonal CONFIDENTIAL stamp.

Processing runs entirely in your browser. PDF.js counts pages via getPdfPageCount; pdf-lib writes the overlay on each selected page. Choose all pages or a subset via parsePageRange. Opacity, rotation, font size, and a diagonal preset give you the classic corner-to-corner stamp without desktop software. The 50 MB upload cap from validatePdfUpload keeps save operations responsive. Nothing is uploaded to a server.

Most watermarks take under two minutes from upload to download. Text mode is fastest; image mode needs a PNG ready.

1. Upload your PDF - Drag and drop or click Choose PDF File. validatePdfUpload enforces the 50 MB cap and confirms the file is a PDF before pdf-lib loads. PDF.js reports page count immediately.
2. Choose text or image watermark - Text mode: enter custom string, set font size, opacity (10–100%), and rotation or enable Diagonal for -45°. Image mode: upload a PNG logo; the tool scales it to roughly half page width by default. One mode per run - re-upload the output to stack a second layer if needed.
3. Select all pages or a page range - All pages stamps uniformly across the document. Page range accepts 2, 4-6 syntax via parsePageRange. Pages you omit stay unchanged - useful when only appendix sheets need REV B.
4. Apply and download the watermarked PDF - Click Apply Watermark, wait for local processing, then Download. Original file on disk stays untouched; you always get a separate output file.

A startup founder exports a 12-page investor deck from Google Slides. Advisors need to review financial projections under NDA, but nothing on the PDF says the deck is confidential or draft. Forwarded slides could be mistaken for final materials posted to a data room. A diagonal CONFIDENTIAL stamp at low opacity solves the labeling problem without blurring charts.

Steps on this page: upload the deck, confirm twelve pages, keep Text mode, enter CONFIDENTIAL, set opacity to 30%, enable Diagonal (-45°), choose All pages, click Apply Watermark, then Download. Partners immediately see draft status while underlying charts and text remain sharp because pdf-lib draws vector text - no screenshot workflow. If only slides 2–11 need marking, switch to Page range and enter 2-11 while leaving the title slide clean for presentation mode.

Pick text for words like CONFIDENTIAL, image for logos, and compressor only when file size - not labeling - is the problem.

Text watermarks add the fewest bytes and scale cleanly at any zoom. Image watermarks look professional for logos but increase file size with PNG resolution. Neither replaces encryption or access control. Run compressor after watermarking if email rejects the attachment - compression does not remove the stamp.

These are the failures the UI surfaces on purpose, plus jobs this page will not pretend to do.

• Not DRM. Simple overlays can be removed in desktop editors. Watermarks deter casual misuse; they do not encrypt content or prevent copying.
• Invalid upload. Non-PDF files and files over 50 MB are rejected by validatePdfUpload before processing starts.
• Empty page range. Typos like page 99 on a 10-page doc yield zero pages; enter at least one valid index.
• Image mode requires PNG. JPG logos must be converted to PNG first. SVG and WebP are not accepted in image mode.
• Encrypted PDFs. pdf-lib cannot load password-locked files without credentials. Unlock locally before uploading.
• Long text may clip. Very long strings at large font sizes can extend past page edges. Shorten the label or reduce font size.
• One mode per run. Text and image watermarks are not combined in a single click. Re-upload the output to stack layers.
• Memory on huge files. Files near 50 MB may spike RAM during pdfDoc.save(). Close other tabs if the browser warns about memory.
• Not redaction. Watermarks do not remove underlying text. Use proper redaction tools when content must be deleted, not merely labeled.

PDF watermarking on this page runs entirely in your browser. pdf-lib and PDF.js load from the same origin as the app; your document bytes are never POSTed to an API, never written to server logs, and never indexed. Suitable for confidential drafts, medical summaries, and legal previews when cloud upload is not permitted. Clear downloads from shared workstations when finished.

We do not persist uploads in localStorage. Closing the tab discards in-memory state except any file you explicitly downloaded. No account means no cross-device history. Uploaded PNG logos for image mode are read once into memory and embedded into the PDF - they are not stored on our servers because there are no servers in the processing path.