# Add Watermark — Technical Tool Documentation > **Summary:** Stamp custom text across every page with opacity, color, angle, and size controls. > **Tool Route:** `/tools/watermark.html` > **Visual Guide Route:** `/guides/watermark-pdf/` > **Category:** Edit PDF > **Processing Architecture:** 100% Client-Side. Zero server uploads. --- ## 1. What the Tool Does Add Watermark draws the text you provide across every page using the selected style settings. **Requirements & Constraints:** One readable PDF and non-empty watermark text are required. This is an existing document feature, separate from PDFHub’s developer panel. --- ## 2. When to Use It Use **Add Watermark** whenever you need to perform client-side edit pdf operations without uploading confidential records to third-party cloud servers. **Ideal Scenarios:** - Working on personal identity records, banking statements, medical filings, or NDAs requiring 100% local confidentiality. - Fast offline or low-bandwidth processing directly in your web browser. - Universal cross-platform document operations on Windows, macOS, Linux, Android, or iOS. --- ## 3. Key Implemented Features - **Engine Architecture:** `pdf-lib (page.drawText with rotation & opacity)` - **Zero Server Uploads:** Processing executes directly within client browser memory. - **Instant Processing:** Fast execution powered by WebAssembly and native HTML5 APIs. - **Review Previews:** Visual feedback and progress indicators confirm results prior to saving. - **No Sign-up / No Watermarks:** Full functionality with zero paywalls or forced branding. --- ## 4. Supported Input Files - **Primary Input:** Single PDF document (.pdf) - **Validation:** Files are validated in the browser prior to parsing. --- ## 5. Supported Output Files - **Output Format:** Watermarked PDF document (watermarked.pdf) - **MIME Types:** `application/pdf` (or appropriate image/text/zip formats). --- ## 6. File Size & Memory Limits - **Recommended Bounds:** Client RAM bound - **Technical Context:** Modern browser tabs enforce memory quotas (typically 1.5 GB to 2 GB per tab). PDFHub handles documents comfortably within standard browser memory limits. For files exceeding 150 MB or 1,000 pages, splitting into smaller sections is recommended. --- ## 7. Step-by-Step Instructions 1. **Upload a PDF and enter the text to stamp.** 2. **Choose font size, opacity, color, and angle.** 3. **Select Add Watermark.** 4. **Review every page for readability and placement before sharing.** --- ## 8. Required User Inputs & Controls - **File Upload Area (`#drop` / `#fin`):** Click to open native file browser or drag and drop supported files. - **Tool Options (`#opts`):** Dynamic settings panel configuring parameters, page ranges, or compression levels. - **Execution Button (`Add Watermark (#goBtn)`):** Triggers client-side processing pipeline. - **Reset Button:** Clears loaded files and resets workspace to pristine state. --- ## 9. Processing Behavior & Execution Pipeline Calculates page center coordinates, computes bounding box of watermark text string, applies rotation angle (45° diagonal or 0° horizontal), sets opacity transparency (0.1 to 0.8), stamps text across every page, and saves PDF. --- ## 10. Expected Output & Download Verification - Upon successful execution, the interface triggers an automated browser download via `downloadBlob()` or opens a result review modal. - Users can verify file size, page count, and visual rendering before finalizing the download. --- ## 11. Practical Example Use Case Stamping "CONFIDENTIAL", "DRAFT", or company copyright text across sensitive business documents before circulation. --- ## 12. Common Errors & Troubleshooting - **Issue:** If the text is hard to see, increase opacity or choose a contrasting color. - **Issue:** If the output fails, retry with a readable unencrypted PDF. - **Avoid:** Using text that covers critical content. - **Avoid:** Forgetting that the mark is applied to every page. - **Tip:** Setting opacity too high (1.0) obscuring text underneath. Solution: Use 0.15 to 0.3 for subtle background watermark. --- ## 13. Privacy & Data Handling Architecture - **Local Processing:** 100% Client-Side. Zero server uploads. - **Browser Memory:** Document bytes reside temporarily in `ArrayBuffer` memory and are garbage collected when the browser tab is refreshed or closed. - **Cookies & Telemetry:** PDFHub sets zero tracking cookies, zero analytics beacons, and stores zero personal document data. --- ## 14. Frequently Asked Questions (FAQ) #### Q: Can I watermark only selected pages? **A:** The current tool applies it to every page. #### Q: Does PDFHub add developer branding as a watermark? **A:** No. User-entered watermark text is the only watermark feature. --- ## 15. Related PDFHub Tools - [Add Page Numbers Documentation](page-numbers.md) - [Edit PDF Documentation](edit-pdf.md) - [Protect PDF Documentation](protect-pdf.md) --- ## 16. Links & Resources - **Launch Live Tool:** [Open Add Watermark in PDFHub](../../tools/watermark.html) - **Visual Tutorial:** [View Add Watermark Visual Guide](../../guides/watermark-pdf/) - **All Tools Master Reference:** [All Tools Reference](../all-tools-reference.md) - **Master Documentation Index:** [Documentation Index](../documentation-index.md) --- ## 17. Visual Walkthrough & Interface Screenshots ### Step 1: Open Add Watermark - **Interface Control:** `Upload Drop Zone (#drop)` - **What You See:** The upload drop area accepts any PDF document. - **What to Do:** Open Add Watermark to stamp copyright notices, confidentiality tags, or company names. - **Practical Pro-Tip:** Watermarks protect intellectual property and identify draft or confidential versions. ![Add Watermark Step 1 - Open Add Watermark](../images/watermark-pdf-step-1.png) ### Step 2: Upload PDF Document - **Interface Control:** `File Browser (#fin)` - **What You See:** The document loads and total page count is displayed. - **What to Do:** Select your PDF document from your storage. - **Practical Pro-Tip:** Watermarks are stamped across all pages uniformly in one pass. ![Add Watermark Step 2 - Upload PDF Document](../images/watermark-pdf-step-2.png) ### Step 3: Enter Watermark Text - **Interface Control:** `Text Input (#wtext)` - **What You See:** The input updates and pre-renders the stamp text. - **What to Do:** Type your custom watermark text (e.g. "CONFIDENTIAL", "DRAFT", or your company name). - **Practical Pro-Tip:** Keep text concise (1-3 words) for the clearest diagonal stamp. ![Add Watermark Step 3 - Enter Watermark Text](../images/watermark-pdf-step-3.png) ### Step 4: Adjust Size, Opacity & Angle - **Interface Control:** `Sliders (#fsize, #opacity, #angle)` - **What You See:** Adjusting opacity ensures the watermark is clearly visible without obscuring underlying text. - **What to Do:** Set font size (e.g. 48pt), opacity slider (e.g. 25%), and diagonal angle (e.g. 45°). - **Practical Pro-Tip:** A 45-degree diagonal angle runs across the full body of the page for maximum security. ![Add Watermark Step 4 - Adjust Size, Opacity & Angle](../images/watermark-pdf-step-4.png) ### Step 5: Select Watermark Color - **Interface Control:** `Color Picker (#color)` - **What You See:** Color options adapt to contrast effectively against white page backgrounds. - **What to Do:** Pick a color for your stamp (e.g. Gray, Red, or Blue). - **Practical Pro-Tip:** Semi-transparent red (#e53e3e) provides an unmistakable confidentiality warning. ![Add Watermark Step 5 - Select Watermark Color](../images/watermark-pdf-step-4.png) ### Step 6: Click Add Watermark - **Interface Control:** `Action Button (#goBtn)` - **What You See:** The client-side engine embeds semi-transparent vector text over each page canvas. - **What to Do:** Click the primary "Add Watermark" button. - **Practical Pro-Tip:** The watermark is baked into the document graphics state. ![Add Watermark Step 6 - Click Add Watermark](../images/watermark-pdf-step-4.png) ### Step 7: Review Stamped Pages & Download - **Interface Control:** `Preview Section & Download (#generatedPreview, #dlModal)` - **What You See:** The preview displays your diagonal watermark stamped across the pages. - **What to Do:** Inspect the watermarked pages in the preview viewer, then click "Download". - **Practical Pro-Tip:** Your protected document is now ready for safe distribution. ![Add Watermark Step 7 - Review Stamped Pages & Download](../images/watermark-pdf-step-4.png)