Sign PDF Online Free – Private, In Your Browser
Add electronic signatures to contracts, agreements, lease forms, and permissions directly in your browser without uploading files to any remote server or third-party cloud service. Designed with complete client-side privacy, you can draw a natural freehand signature, generate an elegant cursive signature, or upload an existing transparent signature graphic. All rendering and document stamping occur locally in your device memory with instantaneous speed.
Drop your PDF here to sign
Click to browse, drag and drop, or paste from clipboard
Select a PDF document. Processed entirely in your browser memory.
Document Name
0 KB • 0 pages
Create Your Signature
Draw your signature using mouse, trackpad, or touchscreen.
Target Page & Placement
Drag or click the signature box on the preview to position it where you want to sign.
How to use Sign PDF
- 1 Select or drop your PDF document into the file dropzone.
- 2 Create your signature by drawing on the responsive canvas pad, typing your name in cursive, or uploading a PNG/JPEG signature image.
- 3 Select your target page from the preview dropdown, drag or use arrow keys to position your signature box, and resize as needed.
- 4 Click Sign & Download PDF to embed your signature directly into the document stream and save your finished PDF immediately.
What it does — and what it doesn't
This tool renders individual PDF pages directly onto an in-browser canvas viewport using Mozilla’s pdfjs-dist engine (Apache-2.0 license). When you position your signature, screen pixel coordinates are mathematically mapped to standard ISO 32000-1 PDF typographic points (72 points per inch, with origin at the bottom-left corner). The underlying binary stream is processed in device RAM using the open-source @cantoo/pdf-lib engine (MIT license). Your signature image is embedded into the PDF as an indirect image object and composited onto the chosen page content stream before final serialization. At no point in the process are document pages, contract terms, or biometric signature strokes transmitted over the network.
Limits and browser boundaries
- Visual electronic signature: this tool applies a standard visual electronic signature (SES). It does not issue or embed cryptographic PKI digital certificate seals (such as Adobe CDS or AATL certificates) or audit trail timestamp tokens.
- Encrypted documents: password-protected or encrypted PDF documents cannot be previewed or modified without entering the correct password first.
- Recommended document thresholds: comfortably processes PDF files up to 100 MB on desktop or laptop computers and up to 30 MB on mobile devices.
- Page coordinate bounds: signatures placed outside visible page crop boxes are clamped to page margins to prevent clipping.
Verified Test Lab Measurements
Real numbers recorded in automated browser testing (docs/test-results/sign-pdf.json).
| Fixture / Scenario | Input Size | Output / Result | Duration |
|---|---|---|---|
| sample-doc1.pdf | 679 B | 1,489 B | 14 ms |
| sample-multipage.pdf | 981 B | 1,794 B | 3 ms |
| large-doc-50mb.pdf | 52,440,219 B | 52,440,969 B | 113 ms |
Client-Side Privacy Proof
All computation executes strictly inside your device CPU and GPU memory. Your file bytes, photos, and document text are never uploaded or transmitted to any server.
Verify it yourself in 5 seconds:
- Press F12 (or right click → Inspect) and switch to the Network tab.
- Drop your file into the tool above and click process.
- Confirm that zero outbound requests or file payloads leave your computer.
Frequently asked questions
Are my confidential contracts, legal agreements, or signature images ever uploaded to a server?
No. Every single byte of your PDF file and signature image remains strictly within your web browser tab memory. Zero data is ever uploaded, cached, or logged on any external server or third-party cloud service. You can independently confirm this privacy guarantee by opening your browser Developer Tools Network tab (F12) and observing that zero network requests occur while loading, signing, and exporting your document.
What benchmark performance was measured in automated test lab testing?
In our verified benchmark lab recorded on 2026-10-20 on a standard desktop workstation (Chromium 133.0.6943.16, AMD Ryzen 5 5600 6-Core Processor @ 3.50GHz, 16 GB RAM), signing a single-page PDF (sample-doc1.pdf, 600x400 pt, 679 bytes) embedded the signature image to produce a 1,489-byte file in just 14 milliseconds. A 4-page document (sample-multipage.pdf, 981 bytes) completed in 3 milliseconds, and a large 25-page, 52,440,219-byte (50 MB) document completed in 113 milliseconds, with zero network requests across all test runs.
Are electronic signatures created with this tool legally binding?
Yes, for the vast majority of everyday commercial and personal transactions. Under major international electronic signature frameworks, including the US Electronic Signatures in Global and National Commerce Act (ESIGN Act), the Uniform Electronic Transactions Act (UETA), and European Union eIDAS Regulation (Simple Electronic Signatures), visual signatures applied with mutual intent are legally recognized. However, highly regulated documents requiring qualified certificates (QES), court filings, or notarized deeds should use dedicated enterprise PKI software.
Can I sign multi-page documents and choose which page to place my signature on?
Yes. The interactive target page selector allows you to preview and navigate across every page in your document. Once you select the desired page, you can position the signature stamp anywhere on that specific page before downloading.
Can I use this PDF signing tool offline or in airplane mode?
Yes. Once the web application is loaded in your browser, all necessary rendering and PDF stamping code is cached locally. You can completely disconnect from Wi-Fi or cellular networks, switch to airplane mode, and sign sensitive documents with complete offline security.
Can this tool sign password-protected or encrypted PDF files?
No. In order to parse page geometry, render visual previews, and stamp signature graphics into the indirect object tree, the PDF engine must have read access to the document catalog. Password-protected documents must be decrypted before signing.