OptiDrop

Add Watermark to PDF — Free Online Tool

Stamp custom text watermarks on every page of your PDF. Choose font size, opacity, rotation angle, and color. Everything runs in your browser — your files never leave your device.

Drop a PDF File Here or Tap to Browse

Supports PDF files up to 100MB

No upload — your PDF stays on your device.
100% Local — your file never leaves this device

Related Tools →

Compress PDF

Reduce PDF file size while keeping quality. Perfect before sharing.

JPG to PDF

Convert images into a single PDF document for easy sharing.

PDF to JPG

Extract pages from a PDF as individual JPG images.

Add Text Watermarks to PDF Online — Free, No Upload Required

OptiDrop's PDF Watermark tool lets you add professional text watermarks to your PDF documents in seconds. Whether you need to stamp "CONFIDENTIAL" on legal documents, add "DRAFT" to work-in-progress files, or brand your PDFs with a company name, our tool handles it all. Unlike other online watermark tools, OptiDrop processes everything locally in your browser — your PDFs are never uploaded to any server, making it completely safe for sensitive documents like contracts, financial reports, and intellectual property.

Full Customization Control

You have complete control over how your watermark looks. Adjust the font size from 12px to 120px for anything from subtle corner stamps to bold page-spanning overlays. Set opacity from 10% for barely-visible background marks to 100% for prominent text. Rotate the watermark at any angle from 0 to 360 degrees — the classic diagonal watermark at 45 degrees is just a slider away. Choose any color to match your branding or make the watermark stand out.

Watermark Every Page Automatically

The watermark is automatically applied to every page of your PDF, centered on the page regardless of page size or orientation. Whether your document has 1 page or 500 pages, each one gets the same consistent watermark. This is ideal for batch-processing documents that need uniform branding or confidentiality markings across all pages.

How PDF Watermarking Works

Our tool uses the pdf-lib JavaScript library to read your PDF, embed a standard font, and draw the watermark text on each page using the drawText() method with your chosen font size, color (with opacity), rotation angle, and centered positioning. The modified PDF is then generated in memory and offered for download. The entire process happens in your browser — no server uploads, no file storage, no privacy concerns.

Frequently Asked Questions

Yes. OptiDrop's PDF Watermark tool lets you fully customize the watermark text, font size (12–120px), opacity (10%–100%), rotation angle (0°–360°), and text color. You can create subtle background stamps or bold overlay watermarks depending on your needs.
Yes. The watermark is applied to every page of your PDF automatically. Each page gets the same watermark centered on it, regardless of page size or orientation. This ensures consistent branding across your entire document.
Absolutely. Your PDF never leaves your device. All watermarking is done locally in your browser using the pdf-lib JavaScript library. No data is uploaded to any server, making it completely safe for confidential documents like contracts, invoices, and legal papers.
OptiDrop can handle PDFs up to 100MB. Since all processing happens in your browser, the actual limit depends on your device memory. Most modern devices handle files with hundreds of pages without any issues.

Last updated: June 2026