How the Free Online PDF Signer Works
The Sign PDF Online tool by DwellixTools is a client-side document utility that allows you to add custom signatures directly onto your PDF files. All processing occurs locally in your browser — no files, code, or signatures are uploaded to our servers.
Many online PDF signers require you to upload your sensitive legal documents, contracts, or tax forms to their cloud storage. This tool operates differently:
- Local Preview Rendering: We use Mozilla’s PDF.js rendering engine to draw your PDF pages directly on an HTML5 canvas in your browser.
- Interactive Signature Overlay: A draggable, resizable, and rotatable signature container is placed on top of the document preview canvas. You position it exactly where you need your signature to go.
- Local PDF Modification: When you click Apply & Download, the pdf-lib library modifies the document’s binary data locally on your computer, embedding your signature image at the exact page, angle, and scaled coordinates you selected.
Key Features
- ✍️ Draw Signature: Draw your signature naturally on a canvas pad using a mouse, trackpad, or touchscreen (fully optimized for mobile tap and drag targets).
- 🔤 Type Cursive Style: Type your name and select from multiple elegant cursive handwriting fonts to generate a professional-looking digital signature.
- 📷 Upload & Auto-Clean Scanned Signature: Upload an existing image of your handwritten signature. The tool automatically removes white or light background paper pixels using a client-side luma filter, rendering a clean transparent signature that blends perfectly onto the page text.
- 🎨 Custom Colors & Thickness: Choose from preset colors (Black, Dark Blue, Red) or pick any custom color from the built-in color spectrum. Adjust ink stroke thickness from 1px to 12px for drawn signatures.
- 🔄 Angle Rotation Handle: Rotate signatures freely in-place on-screen to align them perfectly on angled document lines.
- ↔️ Edge Dragging Overflow: Drag signature containers up to 50% outside the page canvas boundaries to place signatures exactly at the edge or corner margins.
- 📄 Place Multiple Signatures Across Pages: Place multiple signatures on the same page or spread them across different pages. Use the navigation buttons to move between pages and add new signatures as needed.
- 🔒 Browser-Only Privacy: Processes locally in your browser — no files, signatures, or documents are uploaded to our servers or third-party APIs.
How to Sign a PDF Document
- Upload Your PDF: Drag and drop your PDF file into the upload zone, or click to browse and select it.
- Create Your Signature:
- Draw: Draw your signature on the pad. Select your ink color (presets or custom spectrum picker) and adjust the line thickness.
- Type: Click the “Type” tab, type your name, select a cursive handwriting font, and choose your text color.
- Upload: Click the “Upload” tab and choose a signature image from your computer.
- Add to Document: Click the Add to Document button. The signature overlay block will appear on the PDF page.
- Position, Resize, and Rotate:
- Drag the dashed signature box to the line where you want to sign.
- Drag the small blue handle on the bottom-right corner of the box to resize the signature so it fits the line.
- Drag the green handle at the top-center of the box to rotate the signature to match any angled document lines.
- You can drag signature containers up to 50% outside the page canvas boundaries to align signatures precisely at the margins.
- Use the Prev and Next page controls if you need to place the signature on a different page.
- Apply & Download: Click the Apply & Download button in the top right. The browser will compile the signature into your PDF and trigger an immediate file download of the signed document.
Frequently Asked Questions (FAQ)
Are my PDF files or signatures uploaded to your server?
No. All PDF rendering, signature creation, coordinate transformations, and final PDF compilation are executed directly on your device using JavaScript. No documents, files, signatures, or personal data are ever uploaded, sent, or stored on our servers.
Can I verify that no data is transmitted?
Yes. You can open your browser’s Developer Tools (press F12 or Ctrl+Shift+I), select the Network tab, and drag a PDF in. You will see that no network requests are initiated when uploading, signing, or downloading the document.
Is a digitally signed PDF legally binding?
Yes, in many jurisdictions (such as the US ESIGN Act and the European Union eIDAS regulations), electronic signatures on documents are legally recognized. However, this tool provides a basic electronic signature overlay. For high-security, cryptographically-sealed digital signatures or PKI-based certificates, specialized corporate signing platforms are typically required. We recommend verifying specific legal requirements in your jurisdiction.
Can I sign password-protected PDFs?
Yes. If your PDF is locked or encrypted, the tool will securely prompt you to enter the password directly in your browser. The decryption is processed locally on your device to ensure privacy.
Can I sign interactive forms or dynamic PDF layouts?
Yes. The tool flattens all interactive fields (text boxes, drop-downs, and dynamic scripting templates) during compilation. This merges form inputs and signatures into a standardized static layer, making the output PDF compatible with standard readers, browsers, and print services.
Is there a file size limit for uploads?
There is no hard limit on the file size. However, because all computations happen locally in your web browser, very large files (above 20MB) may take a few seconds to compile and download. The tool will display a size warning banner for larger files to notify you.
Can I place multiple signatures on different pages?
Yes. You can add as many signatures as you need. Each time you click “Add to Document”, a new signature box is created. You can drag, resize, and delete them individually. If you navigate to other pages, you can add more signatures to those pages as well. When you click Apply & Download, the tool will compile all placed signatures across all pages into the final PDF in a single download.