Sign Several Times

Introduction

Sometimes it is needed to sign a PDF document by several signees. The PDF format does not support parallel signatures but you have to simply restart the signature process for each signee. 

Example

To sign a PDF document several times you need to create intermediate versions of the document. Following example shows this as a manual process: 

PHP
<?php
require_once('library/SetaPDF/Autoload.php');

// create a temporary writer
$tempWriter = new SetaPDF_Core_Writer_String();

// create a new document instance
$document = SetaPDF_Core_Document::loadByFilename(
    'files/pdfs/tektown/Laboratory-Report.pdf', $tempWriter
);

// create a signer instance
$signer = new SetaPDF_Signer($document);

// set some signature properties
$signer->setReason('Testing');
$signer->setLocation('SetaPDF-Signer Manual');

// create a signature module
$module = new SetaPDF_Signer_Signature_Module_Cms();
// load the certificate
$certificate = 'file://files/certificates/setapdf-no-pw.pem';
$module->setCertificate($certificate);
$module->setPrivateKey(array($certificate, '' /* no password */));

// sign the document and send the final document to the initial writer
$signer->sign($module);

// now simply re-start the process

// create the final writer
$writer = new SetaPDF_Core_Writer_Http('several-signatures.pdf', true);

// create a new document instance based on the temporary result
$document = SetaPDF_Core_Document::loadByString($tempWriter, $writer);

// create a signer instance
$signer = new SetaPDF_Signer($document);

// set a new signature field name
$signer->setSignatureFieldName('Signature 2');

// set some signature properties
$signer->setReason('Also testing');
$signer->setLocation('SetaPDF-Signer Manual');

// create a signature module
$module = new SetaPDF_Signer_Signature_Module_Cms();
// load the certificate
$certificate = 'file://files/certificates/setapdf-no-pw.pem';
$module->setCertificate($certificate);
$module->setPrivateKey(array($certificate, '' /* no password */));

// sign the document and send the final document to the initial writer
$signer->sign($module);

Unknown signature field name

If you don't want or need to care about the signature field names, just use following logic to get a new unused signature field:

PHP
$field = $signer->addSignatureField();
$signer->setSignatureFieldName($field->getQualifiedName());

All details about creating signature fields are documented here.