Objective-C

PDF Sign Unsigned Signature Field

See more PDF Signatures Examples

Demonstrates how to sign a PDF's unsigned signature field.

Note: This example requires Chilkat v9.5.0.85 or greater.

Objective-C

#import <CkoPdf.h>
#import <CkoJsonObject.h>
#import <CkoCert.h>

BOOL success = NO;

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

CkoPdf *pdf = [[CkoPdf alloc] init];

//  Load a PDF containing an unsigned signature field.
success = [pdf LoadFile: @"qa_data/pdf/unsigned_sig_field/due_diligence.pdf"];
if (success == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

//  A PDF with an unsigned signature field appears in Adobe Acrobat as shown below.
//  (When the mouse pointer is hovered over the field, a tooltip will likely show a message
//  such as "Unsigned signature field (Click to sign)".  
//  This example code will automatically find the unsigned signature field,
//  and signs using your certificate.  It automatically sizes the text to the space alotted
//  for the signature.
//  (image:https://example-code.com/images/unsignedSigField.jpg/endImage)

//  Options for signing are specified in JSON.
CkoJsonObject *json = [[CkoJsonObject alloc] init];

//  In most cases, the signingCertificateV2 and signingTime attributes are required.
[json UpdateInt: @"signingCertificateV2" value: [NSNumber numberWithInt: 1]];
[json UpdateInt: @"signingTime" value: [NSNumber numberWithInt: 1]];

//  We don't specify the page or a specific location because Chilkat will automatically
//  find the unsigned signature field and use its location and size and will scale the
//  signatures visual appearance (text + graphics) to the correct size required to fit.
//  We only need to indicate the desire to fill the unsigned signature field.
[json UpdateBool: @"appearance.fillUnsignedSignatureField" value: YES];

//  Starting in Chilkat v9.5.0.90, if a PDF contains multiple unsigned signature fields,
//  the field to be signed can be chosen by name:
//  To list unsigned signature fields, see this example: List PDF Unsigned Signature Fields
[json UpdateString: @"unsignedSignatureField" value: @"doctor_signature"];

//  Note: If the PDF document contains multiple unsigned signature fields, Chilkat will 
//  sign the 1st one found. 

//  In this example, the appearance of the digital signature will contain three lines:
//  1) The signing certificate's common name
//  2) The current date/time
//  3) Some arbitrary text.
//  The keyword "cert_cn" is replaced with the Certificate's Subject Common Name.
//  The keyword "current_dt" is replaced with the current date/time.
//  Any number of appearance text lines can be added.
[json UpdateString: @"appearance.text[0]" value: @"Digitally signed by: cert_cn"];
[json UpdateString: @"appearance.text[1]" value: @"current_dt"];
[json UpdateString: @"appearance.text[2]" value: @"The crazy brown fox jumps over the lazy dog."];

//  This signature will include one of the built-in SVG graphics (green-check-grey-circle).
[json UpdateString: @"appearance.image" value: @"green-check-grey-circle"];
[json UpdateString: @"appearance.imagePlacement" value: @"left"];

//  Load the signing certificate. (Use your own certificate.)
CkoCert *cert = [[CkoCert alloc] init];
success = [cert LoadPfxFile: @"qa_data/pfx/myPdfSigningCert.pfx" password: @"secret"];
if (success == NO) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

//  Tell the pdf object to use the certificate for signing.
success = [pdf SetSigningCert: cert];
if (success == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

success = [pdf SignPdf: json outFilePath: @"qa_output/due_diligence_signed.pdf"];
if (success == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

NSLog(@"%@",@"The PDF has been successfully cryptographically signed.");

//  The appearance of the signature appears in Adobe Acrobat as shown below.
//  (image:https://example-code.com/images/signature3.jpg/endImage)