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Add Watermark to PDF

Stamp text or company logos with live opacity, diagonal rotation, and dense tile grid patterns across your document.

Choose a PDF file or drop here

Open file to configure text stamps, logo transparency, rotation angle, and dense tile grids in real time.

Document.pdf

0 MB • 0 Pages

Watermark Text

Font Family

Size: 48pt

Font Color

Opacity & Rotation Angle

Opacity: 25%

Rotation Angle: -45°

Layer Placement

5. Placement & Pattern Mode

6. Target Page Range

Full-Page Continuous Reader

Live Overlay

100%

Free Online PDF Watermark Tool — Protect Documents with Text & Logos

Digital documents and sensitive PDFs can easily be leaked, misattributed, or shared without permission. With SlowPDF Add Watermark to PDF, you can apply custom text stamps (like CONFIDENTIAL, DRAFT, DO NOT SHARE) or company logo watermarks with adjustable transparency, diagonal rotation, and dense repeating tile patterns.

1 How to Add Watermarks to PDF in 3 Easy Steps

Upload PDF Document: Select or drop your multi-page PDF into the upload area.
Customize Watermark: Switch between Text or Logo mode, type your watermark or upload a logo image, adjust opacity, rotation angle, font size, and pattern mode. Watch the live continuous reader update instantly.
Download Watermarked PDF: Click "Apply Watermark & Download PDF". SlowPDF vector embeds your watermark layers inside browser local RAM using WebAssembly.

Why SlowPDF is the Best Private Watermarking Tool

Unlike web services that transmit confidential legal contracts, business plans, or tax records to external cloud servers, SlowPDF executes 100% of PDF processing inside local browser RAM using pdf-lib and WebAssembly.

100% Client-Side Privacy: Your sensitive files and logos never leave your physical device.
Dense Tile Grid Defense: Tile watermarks repeatedly across pages to prevent cropping or unauthorized camera capture.
Layer Control: Choose whether to stamp watermarks over content or behind existing page layers.
Zero Vector Loss: Document typography, form fields, and resolution remain 100% intact.

Next Steps After Watermarking Your PDF

Once your document is watermarked, explore our companion browser tools to further secure and manage your files:

Add 256-bit password encryption with Protect PDF. Reduce file size after embedding company logos with Compress PDF. Insert continuous headers and footers with Add Page Numbers. Modify text directly and annotate pages with Edit PDF.

Frequently Asked Questions

Everything you need to know about watermarking PDFs on SlowPDF.

Upload your PDF to SlowPDF, click one of our quick preset pills (CONFIDENTIAL, DRAFT, SAMPLE, COPY, DO NOT SHARE), adjust opacity and angle, then click 'Apply Watermark & Download PDF'.

Yes! Switch to the 'Image / Logo Watermark' tab, upload any transparent PNG, JPG, or WebP logo, scale it to your desired size, and apply it across your document.

Use our live Opacity slider to set transparency from 5% (ultra-faint) to 100% (solid). Default 25% provides optimal readability while ensuring strong copyright protection.

'Single Center' places one large watermark neatly in the middle of each page. 'Repeated Grid' tiles the watermark repeatedly across the entire page to prevent unauthorized cropping or scanning.

Yes! Toggle between 'Stamp Over Content (High Security)' and 'Stamp Behind Content' in the studio controls.

No. SlowPDF embeds vector text objects or high-resolution PNG bytes directly into PDF page layers using pdf-lib, preserving 100% of original vector clarity.

Never. All document processing and logo embedding happen 100% inside your local device's browser RAM using WebAssembly. No files leave your physical device.

Yes. Choose between 'All Pages', 'Only First Page', or enter a custom range (e.g., 2-10).

Yes! SlowPDF's watermark studio adapts dynamically for mobile devices with a responsive top control dock and full-width continuous page preview.

Yes! SlowPDF is 100% free with zero watermarks, zero limits, and zero mandatory registrations.