(Objective-C) PDF Update or Add XML Metadata

Demonstrates how to add or update the XML metadata stored in a PDF.

Note: This example requires Chilkat v10.1.0 or later.

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#import <CkoPdf.h>
#import <CkoXml.h>
#import <CkoStringBuilder.h>
#import <CkoDateTime.h>
#import <NSString.h>

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

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

// Load a PDF file.
// If the PDF file already has metadata, we'll update it.
// Otherwise this example adds the metadata.
BOOL success = [pdf LoadFile: @"qa_data/pdf/blank_with_metadata.pdf"];
if (success == NO) {
    NSLog(@"%@",pdf.LastErrorText);
    return;
}

CkoXml *xml = [[CkoXml alloc] init];
CkoStringBuilder *sbExisting = [[CkoStringBuilder alloc] init];

BOOL hasMetadata = [pdf GetMetadata: sbExisting];
if (hasMetadata == YES) {
    [xml LoadSb: sbExisting autoTrim: YES];
}
else {

    // Otherwise create the bare minimum XMP metadata.
    xml.Tag = @"x:xmpmeta";
    [xml AddAttribute: @"xmlns:x" value: @"adobe:ns:meta/"];
    [xml AddAttribute: @"x:xmptk" value: @"Adobe XMP Core 9.1-c001 79.675d0f7, 2023/06/11-19:21:16 "];
    [xml UpdateAttrAt: @"rdf:RDF" autoCreate: YES attrName: @"xmlns:rdf" attrValue: @"http://www.w3.org/1999/02/22-rdf-syntax-ns#"];
    [xml UpdateAttrAt: @"rdf:RDF|rdf:Description" autoCreate: YES attrName: @"rdf:about" attrValue: @""];
    [xml UpdateAttrAt: @"rdf:RDF|rdf:Description" autoCreate: YES attrName: @"xmlns:xmp" attrValue: @"http://ns.adobe.com/xap/1.0/"];
    [xml UpdateAttrAt: @"rdf:RDF|rdf:Description" autoCreate: YES attrName: @"xmlns:dc" attrValue: @"http://purl.org/dc/elements/1.1/"];
    [xml UpdateAttrAt: @"rdf:RDF|rdf:Description" autoCreate: YES attrName: @"xmlns:xmpMM" attrValue: @"http://ns.adobe.com/xap/1.0/mm/"];
    [xml UpdateAttrAt: @"rdf:RDF|rdf:Description" autoCreate: YES attrName: @"xmlns:pdf" attrValue: @"http://ns.adobe.com/pdf/1.3/"];
    [xml UpdateAttrAt: @"rdf:RDF|rdf:Description" autoCreate: YES attrName: @"xmlns:xmpRights" attrValue: @"http://ns.adobe.com/xap/1.0/rights/"];

    CkoDateTime *dt = [[CkoDateTime alloc] init];
    [dt SetFromCurrentSystemTime];
    NSString *ts = [dt GetAsTimestamp: YES];

    [xml UpdateChildContent: @"rdf:RDF|rdf:Description|xmp:ModifyDate" value: ts];
    [xml UpdateChildContent: @"rdf:RDF|rdf:Description|xmp:CreateDate" value: ts];
    [xml UpdateChildContent: @"rdf:RDF|rdf:Description|xmp:MetadataDate" value: ts];

    [xml UpdateChildContent: @"rdf:RDF|rdf:Description|xmp:CreatorTool" value: @"My Custom Application"];
    [xml UpdateChildContent: @"rdf:RDF|rdf:Description|dc:format" value: @"application/pdf"];

    CkoStringBuilder *sbDocId = [[CkoStringBuilder alloc] init];
    [sbDocId Append: @"uuid:"];
    [sbDocId AppendUuid: YES];
    [xml UpdateChildContent: @"rdf:RDF|rdf:Description|xmpMM:DocumentID" value: [sbDocId GetAsString]];

    CkoStringBuilder *sbInstanceId = [[CkoStringBuilder alloc] init];
    [sbInstanceId Append: @"uuid:"];
    [sbInstanceId AppendUuid: YES];
    [xml UpdateChildContent: @"rdf:RDF|rdf:Description|xmpMM:InstanceID" value: [sbInstanceId GetAsString]];

}

// Add our custom metadata tags to either the existing XML metdata, or the newly created metadata.
[xml UpdateAttrAt: @"rdf:RDF|rdf:Description" autoCreate: YES attrName: @"xmlns:zf" attrValue: @"urn:ferd:pdfa:CrossIndustryDocument:invoice:1p0#"];
[xml UpdateAttrAt: @"rdf:RDF|rdf:Description" autoCreate: YES attrName: @"rdf:about" attrValue: @" "];
[xml UpdateChildContent: @"rdf:RDF|rdf:Description|zf:ConformanceLevel" value: @"BASIC"];
[xml UpdateChildContent: @"rdf:RDF|rdf:Description|zf:DocumentFileName" value: @"ZZZZZZ-invoice.xml"];
[xml UpdateChildContent: @"rdf:RDF|rdf:Description|zf:DocumentType" value: @"INVOICE"];
[xml UpdateChildContent: @"rdf:RDF|rdf:Description|zf:Version" value: @"1.0"];

// Create a new PDF with the updated metadata.
CkoStringBuilder *sb = [[CkoStringBuilder alloc] init];
[xml GetXmlSb: sb];
success = [pdf UpdateMetadata: sb outFilePath: @"c:/temp/qa_output/out.pdf"];
if (success == YES) {
    NSLog(@"%@",@"Success");
}
else {
    NSLog(@"%@",pdf.LastErrorText);
}

// To see the metadata in Adobe Acrobat DC,
// 1) Open the PDF.
// 2) CTRL-D to show the Document Properties dialog.
// 3) In the dialog, click on the "Additional Metadata" button.
// 4) In the Additional Data dialog, click on "Advanced"
// 5) Expand the namespace tree for the metadata you added.

NSLog(@"%@",@"OK");