PDF Add Stamps
Add stamps to PDF files online for free. Apply "Approved", "Draft", "Confidential" stamps or custom text. All processing in your browser.
How to Use
Add stamps to your PDF in four steps:
- Upload your PDF — Drag and drop or click to browse. The tool reads the file locally in your browser.
- Choose a stamp — Select a preset (CONFIDENTIAL, DRAFT, APPROVED, etc.) or type custom text. Adjust font size, opacity, rotation, color, and position.
- Set page range (optional) — Specify which pages receive the stamp (e.g., "1-5,8"). Leave blank to stamp all pages.
- Apply and download — Click Add Stamp to process. Download the stamped PDF when ready.
All processing runs in your browser using pdf-lib. No files leave your device.
About This Tool
PDF stamping overlays text onto existing page content without altering the underlying document structure. Unlike watermarking during document creation, post-hoc stamping adds visible annotations to finalized documents — marking them as drafts, copies, or confidential materials for distribution control.
How pdf-lib draws text stamps
The tool uses pdf-lib's page.drawText() method with a graphics state that sets opacity via the opacity parameter. Rotation is applied through the rotate option using degrees() from pdf-lib. The text is positioned relative to the page dimensions, with the coordinate origin at the bottom-left corner of each page.
PDF coordinate system and text positioning
PDF uses a bottom-left origin where Y increases upward, measured in points (1 point = 1/72 inch). An A4 page is 595 × 842 points. To center text, the tool calculates the text width using the embedded font's widthOfTextAtSize() method, then positions the text at (pageWidth - textWidth) / 2 horizontally and pageHeight / 2 vertically. When rotation is applied, the coordinate system rotates around the text's anchor point.
StandardFonts and embedding
pdf-lib provides 14 built-in PDF standard fonts (Helvetica, Times Roman, Courier, etc.) that don't require font file embedding — they're guaranteed to be available in every PDF viewer. This keeps the output file size minimal since no font data needs to be added to the document. The trade-off is limited character support — standard fonts cover Latin-1 characters but not CJK, Arabic, or other complex scripts.
Opacity and the PDF graphics state
PDF transparency is controlled through graphics state parameters, specifically the ca (non-stroking opacity) and CA (stroking opacity) values in an ExtGState dictionary. pdf-lib abstracts this into a simple opacity parameter. A value of 0.3 makes the stamp clearly visible as an overlay while allowing the underlying document content to remain readable — the standard approach for document watermarks.
All processing happens client-side in your browser. For removing existing stamps or watermarks, the PDF would need to be rasterized through PDF Adjust Colors. For adding page numbers instead of stamps, use PDF Add Page Numbers.
Why Use This Tool
Adding stamps to PDFs serves several professional and legal purposes:
- Document classification — Marking documents as CONFIDENTIAL, INTERNAL, or PUBLIC ensures recipients understand handling requirements. Many compliance frameworks (ISO 27001, SOC 2) require visible classification labels on sensitive documents.
- Draft management — DRAFT stamps prevent preliminary versions from being mistaken for final documents. This is standard practice in legal, engineering, and publishing workflows where multiple revision cycles produce many intermediate versions.
- Copy control — COPY stamps distinguish duplicates from originals in legal and notarial contexts. Court filings often require copies to be clearly marked to distinguish them from certified originals.
- Approval workflows — APPROVED, FINAL, and VOID stamps provide visible status indicators. While not cryptographically secure, they communicate document status at a glance during review cycles.
- Distribution tracking — Custom stamps with recipient names, dates, or tracking numbers help identify the source of unauthorized document sharing.
Processing locally is essential for stamping — the documents being marked as confidential or draft are by definition sensitive. This tool guarantees they never leave your device.