Protect proprietary documents and stamp confidential notices with our free PDF Watermark Adder. Add custom text watermarks with adjustable opacity, angles, font sizes, and colors across all pages directly in your browser with complete privacy.
Upload your PDF file into the visual watermark overlay designer.
Type custom text or upload logo images, adjust opacity, rotation, and font size.
Click Apply Watermark to stamp overlay graphics onto all pages and download.
Set custom text, opacity levels from 5% to 100%, rotation angles, font size, and text color.
Renders clean vector text directly onto page content streams without rasterizing pages or losing sharpness.
100% client-side execution; PDF files are stamped in local browser memory and never uploaded to remote servers.
Watermarking PDF pages client-side appends text drawing operators (BT, Tj, ET) directly onto individual page content streams. pdf-lib embeds standard bold fonts and calculates text bounding dimensions via font.widthOfTextAtSize().
Rotational transformations and transparency opacities are mapped using Extended Graphics States (/ExtGState) parameters (/ca and /CA dictionaries), rendering smooth semi-transparent watermark overlays centered on each page canvas.
The modified document is re-saved into a new binary ArrayBuffer (pdfDoc.save()). Existing vector paths, form fields, embedded fonts, and raster images remain 100% intact without quality degradation.