PDF Signing

Full reference for PAdES PDF signing — visible and invisible signatures, multi-page, timestamps, and appearance customization.

All features supported

Every PDF signing capability listed below is implemented and working on Mobile App and Desktop Software. Visible appearance options are documented in Signature Customization.

Overview

SecureSign embeds PAdES-compliant digital signatures into PDF documents using the DSC token private key. Supports visible stamps with full appearance customization and invisible signatures for backend-only signing.

Input: base64-encoded PDF or PDF URL (mobile deep link).
Output: signed PDF with embedded signature field and optional visible appearance.
Coordinates use PDF points (1/72 inch); origin is bottom-left of the page.

Platform Support

Feature	Mobile App	Desktop Software	REST API
PDF Sign	Deep link	Deep link	POST /sign/pdf
Visible PDF Signature	Supported	`visible: true`	`visible: true`
Invisible PDF Signature	Supported	`visible: false`	`visible: false`
Multi-Page PDF	`page` field	`page` field	`page` field
Multiple Signatures	Sequential signs	`signatureIndex`	Multiple requests
PDF Verification	Supported	POST /verify/pdf	POST /verify/pdf
PDF Timestamping	TSA option	`timestamp: true`	`timestamp: true`
Position Selection	`position` object	`position` object	`position` object
Custom Appearance	`appearance` object	`appearance` object	`appearance` object

Request Fields

Field	Type	Required	Description
`pdfBase64`	string	Yes*	Base64-encoded PDF (*or `pdfUrl` on mobile)
`visible`	boolean	No	Show visible stamp (default `false`)
`page`	number	When visible	1-based page number for stamp placement
`position`	object	When visible	`{ x, y, width?, height? }` in PDF points
`appearance`	object	No	Visible stamp customization — see Signature Customization
`reason`	string	No	Signing reason metadata (also in appearance)
`location`	string	No	Signing location metadata
`certSerial`	string	No	Pre-select certificate
`timestamp`	boolean	No	Embed TSA timestamp (default `false`)
`signatureIndex`	number	No	Field name suffix for multiple signatures (`Signature2`, etc.)
`callbackUrl`	string	REST only	Server callback URL

Visible vs Invisible

Mode	`visible`	Appearance	Use case
Visible	`true`	`appearance` + `position` required	Forms, contracts, government filings
Invisible	`false`	Ignored	Backend document sealing, audit trails

Multi-Page & Multiple Signatures

Multi-page — set page to the target page number. Each sign operation adds one signature field.

Multiple signatures — sign the output PDF again with incremented signatureIndex. Each pass adds a new signature field without invalidating prior signatures.

{
  "pdfBase64": "JVBERi0x...",
  "visible": true,
  "page": 3,
  "signatureIndex": 2,
  "position": { "x": 72, "y": 120, "width": 220, "height": 80 },
  "appearance": { "templateId": "minimal", "signerName": "Rajesh Kumar" }
}

Examples

const params = new URLSearchParams({
  requestId: crypto.randomUUID(),
  hashBase64: sha256Base64,
  hashAlgo: 'SHA256',
  documentType: 'pdf',
  callbackUrl: 'https://portal.example.gov.in/sign/callback',
  apiKey: 'ss_live_abc123xyz'
});
window.location.href = `securesign://sign?${params}`;
// Add documentBase64 and appearance params to URLSearchParams

const params = new URLSearchParams({
  requestId: crypto.randomUUID(),
  hashBase64: sha256Base64,
  hashAlgo: 'SHA256',
  documentType: 'hash',
  callbackUrl: 'https://portal.example.gov.in/sign/callback',
  apiKey: 'ss_live_abc123xyz'
});
window.location.href = `securesign://sign?${params}`;

curl -X POST https://api.securesign.toolsbots.com/v1/sign/pdf \
  -H 'Authorization: Bearer ss_live_abc123xyz' \
  -H 'Content-Type: application/json' \
  -d '{"pdfBase64":"JVBERi0x...","visible":true,"page":1,"position":{"x":72,"y":120,"width":240,"height":90},"appearance":{"templateId":"standard","signerName":"Rajesh Kumar"},"callbackUrl":"https://portal.example.gov.in/callback"}'

Response

{
  "success": true,
  "signedPdfBase64": "JVBERi0x...",
  "signatureField": "Signature1",
  "appearanceApplied": {
    "templateId": "gov_portal",
    "visible": true,
    "page": 1,
    "signerName": "Rajesh Kumar",
    "signedAt": "2026-06-22T10:30:00+05:30"
  }
}

Errors

Code	Cause	Resolution
`SS_PDF_INVALID`	Corrupt or non-PDF input	Verify base64 encoding and PDF structure
`SS_PAGE_OUT_OF_RANGE`	`page` exceeds document pages	Check page count
`POSITION_OUT_OF_BOUNDS`	Stamp extends past page edge	Adjust `position` coordinates
`APPEARANCE_REQUIRES_VISIBLE`	`appearance` with `visible: false`	Set `visible: true`
`SS_PDF_ALREADY_SIGNED`	Signature field name collision	Increment `signatureIndex`