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SignatureAPI works on any device with a browser. However, standard letter-size PDFs can be difficult to read and sign on small screens. This guide covers how to optimize documents for mobile signing and set up in-person signing on shared devices like tablets.

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Optimizing documents for mobile

The key to mobile-friendly signing is creating documents with larger page dimensions and bigger text so the content fills the screen without excessive zooming.

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Page size and layout

Instead of standard letter size (8.5” x 11”), create your PDF with a taller, narrower aspect ratio that matches a phone screen. A single-column layout with large text works best. Recommended approach:
  • Page size: Use a custom page size around 6” x 10” or similar portrait ratio.
  • Font size: Use 16pt or larger for body text.
  • Margins: Use generous margins (at least 0.75”) so content does not crowd the edges.
  • Single column: Avoid multi-column layouts or side-by-side content.
  • Signature place height: Use the default height of 60 for signature places so they are easy to tap and sign.

Mobile-friendly DOCX example

Download an example document optimized for mobile signing.

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Tips for generating mobile-friendly PDFs

If you generate PDFs programmatically:
  • Set the page dimensions in your PDF library to match a mobile-friendly ratio.
  • Keep each page short with minimal content so the signer does not need to scroll within a page.
  • Place signature fields near the bottom of the page where thumbs naturally reach.
If you use DOCX templates:
  • Set the page size in Word under Layout > Size > More Paper Sizes.
  • Use a large font size and generous line spacing.

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In-person signing on shared devices

For scenarios where signers are physically present (point of sale, front desk, clinic check-in), you can present the signing ceremony on a shared tablet or kiosk.

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Setup

Use custom authentication and embed the ceremony in your application. This lets you:
  • Control when the ceremony is shown on the device.
  • Skip the email invitation flow entirely.
  • Record who authenticated the signer in the audit log.
// POST https://api.signatureapi.com/v1/envelopes
// X-API-Key: key_live_...
// Content-Type: application/json

{
    "title": "Check-In Agreement",
    "documents": [ //... ],
    "recipients": [
        {
            "type": "signer",
            "key": "visitor",
            "name": "Jane Doe",
            "email": "jane@example.com",
            "delivery_type": "none",
            "ceremony": {
                "authentication": [
                    {
                        "type": "custom",
                        "provider": "Front Desk",
                        "data": {
                            "verified_by": "staff_member_42",
                            "device": "lobby_tablet_1"
                        }
                    }
                ],
                "embeddable_in": ["https://kiosk.yourapp.com"]
            }
        }
    ]
}

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Between signers

After one signer completes, your application should clear the ceremony from the screen before presenting the next signer’s ceremony. Do not reuse ceremony URLs between different signers.

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