(Objective-C) PDF Signature Page Location

See more PDF Signatures Examples

This example demonstrates how to specify the location of a PDF signature on a page.

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

Chilkat Objective-C Library Downloads MAC OS X (Cocoa) Libs iOS Libs

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

// 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 to be signed.
// The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
BOOL success = [pdf LoadFile: @"qa_data/pdf/hello.pdf"];
if (success == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

// 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]];

// When cryptographically signing a PDF, the signature's appearance can be placed on a specific
// page in the PDF document, and at a specified location on the page.
// The 1st page of the PDF document is page number 1 (we don't use 0-based numbering for PDF page numbers).
// The PDF object has a NumPages property, so we can use it to sign on the last page of the PDF.
[json UpdateInt: @"page" value: pdf.NumPages];

// appearance.y and appearance.x JSON properties control the x,y location of the signature.
// The "appearance.y" can be "top" or "bottom".
// The "appearance.x" can be "left", "middle", or "right".
// It is also possible to specify exact PDF location in user space coordinates, which is discussed below.
[json UpdateString: @"appearance.y" value: @"bottom"];
[json UpdateString: @"appearance.x" value: @"middle"];

// In this example, the fontScale (in combination with the number of appearance text lines and the length of the longest text line),
// automatically determine the width/height of the signature text box. Any included graphic (JPG image or built-in SVG) is automatically
// scaled to fit. It is alternatively possible to specify the desired width/height of the signature rectangle.  In that case
// you would NOT specify a fontScale because Chilkat would automatically chose a font scale to fit the text to the desired rectangle.
// This example demonstrates how to specify the exact width/height of the PDF signature text box.
[json UpdateString: @"appearance.fontScale" value: @"9.0"];

[json UpdateString: @"appearance.text[0]" value: @"Digitally signed by: cert_cn"];
[json UpdateString: @"appearance.text[1]" value: @"current_dt"];
[json UpdateString: @"appearance.image" value: @"document-accepted"];
[json UpdateString: @"appearance.imagePlacement" value: @"left"];
[json UpdateString: @"appearance.imageOpacity" value: @"100"];

// Load the signing certificate. (Use your own certificate.)
CkoCert *cert = [[CkoCert alloc] init];
success = [cert LoadPfxFile: @"qa_data/pfx/myPdfSigningCert.pfx" password: @"pfx_password"];
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/hello_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 here:

// ----------------------------------------------------------------------------------------------------
// *** Scroll down for information about specifying the PDF signature x,y location in user space coordinates.
// ----------------------------------------------------------------------------------------------------



// The x,y coordinates of a PDF page are in "user space", called "points", and there are 72 pointes per inch.
// A PDF page (8.5" x 11") is 612 points wide and 792 points high.
// The bottom left is at 0,0.    The top right is at 612,792.
// 
// To specify the location of a signature rectangle, the "appearance.y" is the y coordinate of the top of the signature rectangle,
// and the "appearance.x" is the x coordinate of the left of the signature rectangle.
// Therefore, to position the signature rectangle at the exact top/left of the page, we do this:

[json UpdateString: @"appearance.y" value: @"792"];
[json UpdateString: @"appearance.x" value: @"0"];

[json UpdateString: @"appearance.text[0]" value: @"Digitally signed again by: cert_cn"];
[json UpdateString: @"appearance.text[1]" value: @"current_dt"];
[json UpdateString: @"appearance.image" value: @"document-accepted"];
[json UpdateString: @"appearance.imagePlacement" value: @"right"];

CkoPdf *pdf2 = [[CkoPdf alloc] init];
success = [pdf2 LoadFile: @"qa_output/hello_signed.pdf"];
success = [pdf2 SetSigningCert: cert];

success = [pdf2 SignPdf: json outFilePath: @"qa_output/hello_signed2.pdf"];
if (success == NO) {
    NSLog(@"%@",pdf2.LastErrorText);
    return;
}

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

// Here we have the PDF with the signature just added at the exact top/left.