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Version: 2.0 (Beta)

Sign PDF (Handwritten Signatures)

Tool ID: sign

Add handwritten signatures, text signatures, or image-based signatures to PDF documents. This tool is for visual/handwritten signatures - for certificate-based digital signatures, see Certificate Signing.

What is PDF Signing?​

There are two types of PDF signatures:

Handwritten/Visual Signatures (This Tool)​

  • Draw your signature with mouse/touchscreen
  • Add signature as text (typed name)
  • Upload signature image (PNG, JPG)
  • Visual appearance only
  • Non-cryptographic

Use For: Signing forms, contracts, letters where a visual signature is needed.

Digital/Certificate Signatures (Different Tool)​

  • Cryptographic signatures using certificates
  • Proves identity and document integrity
  • Cannot be forged
  • Legally binding in many jurisdictions

Use For: Legal documents, contracts requiring authentication, compliance requirements.

Learn More: Certificate Signing Guide

How to Sign PDFs​

Method 1: Draw Your Signature​

  1. Upload PDF - Select document to sign
  2. Navigate to Page - Find where you need to sign
  3. Click "Draw Signature" - Opens signature pad
  4. Draw - Use mouse or touchscreen to draw signature
  5. Position - Drag signature to correct location
  6. Resize - Adjust signature size
  7. Apply - Add signature to PDF
  8. Download - Save signed document

Tips:

  • Use a touchscreen or stylus for best results
  • Draw slowly for smoother lines
  • Click "Clear" to redraw if needed
  • Make signature large enough to be legible

Method 2: Type Your Signature​

  1. Upload PDF
  2. Click "Text Signature"
  3. Type Your Name - Enter text for signature
  4. Choose Font - Select cursive/script font
  5. Position and Size - Adjust placement
  6. Apply - Add to PDF

Best For: Quick signing when handwriting isn't practical.

Method 3: Upload Signature Image​

  1. Upload PDF
  2. Click "Upload Signature"
  3. Select Image - Choose PNG/JPG of your signature
  4. Position and Resize - Place on document
  5. Apply - Add to PDF

Best For: Consistent signature appearance across documents.

Using Pre-stored Signatures​

You can configure Stirling-PDF to load pre-stored signature files for quick access. This is useful for:

  • Consistent signature appearance
  • Quick signing of multiple documents
  • Team/organization signature standards

Configuration: Sign with Custom Files

Signature Options​

Appearance​

Transparency:

  • Make signature background transparent
  • Blend naturally with document

Color:

  • Traditional blue ink
  • Black ink
  • Custom colors

Size:

  • Adjust to fit signature line
  • Maintain aspect ratio
  • Scale up/down as needed

Position​

Placement:

  • Drag and drop to any location
  • Align to signature lines
  • Position relative to form fields

Rotation:

  • Rotate if needed
  • Adjust angle

Pages:

  • Sign on single page
  • Add to multiple pages
  • Different signatures per page

Best Practices​

Creating Good Signatures​

For Drawn Signatures:

  1. Use a stylus or touchscreen if possible
  2. Draw slightly larger than needed (easier to scale down)
  3. Use consistent speed for smooth lines
  4. Practice in signature pad before applying
  5. Keep signature simple (complex signatures may not look good)

For Image Signatures:

  1. Scan or photograph on white paper
  2. High contrast (dark ink, white background)
  3. Crop tightly around signature
  4. Save as PNG with transparent background
  5. High resolution (300 DPI minimum)

Document Signing​

Before Signing:

  1. Read the entire document
  2. Verify all details are correct
  3. Ensure you have authority to sign
  4. Check signature placement locations

While Signing:

  1. Place signature within designated areas
  2. Don't cover important text
  3. Size appropriately for signature line
  4. Add date if required
  5. Add initials if multiple pages

After Signing:

  1. Save original unsigned copy (optional)
  2. Download signed PDF
  3. Verify signature appears correctly
  4. Distribute or submit as needed

Signature Types Comparison​

Visual vs. Digital Signatures​

FeatureVisual Signature (This Tool)Digital Signature (Certificate)
AppearanceHandwritten/imageMay include visual + certificate info
SecurityVisual only, can be copiedCryptographically secure
AuthenticationNo verificationProves signer identity
Tamper DetectionNoneDetects any changes after signing
Legal ValidityVaries by jurisdictionLegally binding in many countries
Use CaseForms, casual documentsContracts, legal documents
SetupNone requiredRequires certificate

When to Use Each​

Use Visual Signing (This Tool) When:

  • ✅ Signing forms and applications
  • ✅ Internal documents
  • ✅ Casual agreements
  • ✅ Documents that just need a visual signature
  • ✅ No cryptographic verification needed

Use Digital Signing (Certificate) When:

  • ✅ Legal contracts requiring authentication
  • ✅ Compliance and regulatory documents
  • ✅ Documents that must prove integrity
  • ✅ Multi-party agreements needing verification
  • ✅ Legally binding signatures required

Multiple Signatures​

Signing as Multiple People​

Option 1: Sequential Signing

  1. First person signs and saves
  2. Second person opens signed PDF
  3. Second person adds their signature
  4. Continue for additional signers

Option 2: Signature Coordination

  1. Each person creates their signature image
  2. One person uploads all signatures
  3. Places each signature in correct location

Team Signatures​

For organizations needing standardized signatures:

  1. Store signature images on server
  2. Configure pre-loaded signatures
  3. Users select from available signatures
  4. Consistent appearance across documents

Setup: Sign with Custom Files

Common Issues​

"Signature looks pixelated"​

Causes:

  • Drew too small and scaled up
  • Low resolution image
  • Compressed too much

Solutions:

  • Draw signature larger
  • Use higher resolution image (300+ DPI)
  • Save as PNG, not JPG

"Signature doesn't match signature line"​

Causes:

  • Signature too large or small
  • Wrong aspect ratio
  • Position slightly off

Solutions:

  • Resize to fit signature line
  • Adjust aspect ratio if needed
  • Zoom in for precise positioning

"Can't draw smooth signature"​

Causes:

  • Using mouse (not ideal for drawing)
  • Drawing too fast
  • No stylus/touchscreen

Solutions:

  • Use touchscreen or stylus if available
  • Draw more slowly
  • Consider uploading signature image instead
  • Use text signature as alternative

Security Considerations​

What Visual Signatures DON'T Provide​

⚠️ No Authentication:

  • Anyone can draw/add any signature
  • No way to verify who actually signed
  • Can be copied from other documents

⚠️ No Tamper Protection:

  • Document can be edited after signing
  • No way to detect changes
  • Signature can be moved/removed

⚠️ Limited Legal Standing:

  • May not be legally binding
  • Jurisdiction-dependent
  • Check local laws and requirements

When Visual Signatures Are Sufficient​

✅ Appropriate For:

  • Internal company forms
  • Consent forms (non-legal)
  • Acknowledgment of receipt
  • Casual agreements
  • Personal documents

❌ NOT Appropriate For:

  • Legal contracts (use digital signatures)
  • Financial documents requiring verification
  • Government/regulatory submissions
  • Documents requiring proof of identity
  • Multi-party agreements needing authentication

Electronic Signature Laws​

Different jurisdictions have different requirements:

US (ESIGN Act):

  • Visual signatures generally accepted
  • Intent to sign is key
  • Record retention required

EU (eIDAS Regulation):

  • Three signature levels: Simple, Advanced, Qualified
  • Visual signatures = Simple Electronic Signatures
  • Limited legal weight compared to qualified signatures

Always:

  • Check local laws and requirements
  • Consult legal counsel for important documents
  • Use digital signatures for legally binding documents

API Usage​

Add signatures programmatically via API:

# This tool is primarily interactive
# For programmatic signing, use certificate signing:
curl -X POST http://stirling-pdf:8080/api/v1/sign/cert \
  -F "fileInput=@document.pdf" \
  -F "certFile=@certificate.p12" \
  -F "password=certpass" \
  -o signed.pdf

See API Documentation for complete endpoint reference.

Summary​

Stirling-PDF's Sign tool provides:

✅ Three signature methods - Draw, type, or upload ✅ Easy positioning - Drag and drop placement ✅ Customizable appearance - Size, color, transparency ✅ Multiple signatures - Sign as multiple parties ✅ Pre-stored signatures - Quick access to saved signatures ✅ No setup required - Start signing immediately

Perfect for forms, applications, and documents needing visual signatures!

Need authentication and legal validity? Use Certificate Signing instead.