import { PdfXmpSchema } from './pdf-xmp-schema';
import { PdfXmpSchemaType } from '../enumerator';
import { PdfXmpMetadata } from './pdf-xmp-metadata';
/**
 * Represents the base schema for PDF document metadata properties.
 * ```typescript
 * // Load an existing PDF document
 * let document: PdfDocument = new PdfDocument(data, password);
 * // Create XMP metadata
 * let xmp: PdfXmpMetadata = new PdfXmpMetadata();
 * // Sets PDF keywords
 * xmp.pdfSchema.keywords = 'sample, pdf, metadata';
 * // Save the document
 * document.save('output.pdf');
 * // Destroy the document
 * document.destroy();
 * ```
 */
export declare class PdfSchema extends PdfXmpSchema {
    private _keywords;
    private _pdfVersion;
    private _producer;
    /**
     * Initializes a new `PdfSchema` instance.
     *
     * @private
     * @param {PdfXmpMetadata} xmp Optional parent PdfXmpMetadata reference.
     */
    constructor(xmp?: PdfXmpMetadata);
    /**
     * Gets the schema type.
     *
     * @returns {PdfXmpSchemaType} The schema type.
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data);
     * // Access the document properties
     * let documentProperties: PdfDocumentInformation = document.getDocumentInformation(false);
     * // Gets the PDF Schema from the XMP metadata
     * let pdfSchema: PdfSchema = xmpMetadata.pdfSchema;
     * // Gets the schema type
     * let schemaType: PdfXmpSchemaType = pdfSchema.schemaType;
     * // Save the document
     * document.save('output.pdf');
     * // Destroy the document
     * document.destroy();
     * ```
     */
    readonly schemaType: PdfXmpSchemaType;
    /**
     * Gets the PDF keywords.
     *
     * @returns {string} The PDF keywords.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Access the document properties
     * let documentProperties: PdfDocumentInformation = document.getDocumentInformation(false);
     * // Gets the xmp metadata
     * let xmpMetadata = documentProperties.xmpMetadata;
     * // Access keywords from PDF schema
     * let keywords: string = xmpMetadata.pdfSchema.keywords;
     * // Destroy the document
     * document.destroy();
     * ```
     */
    /**
    * Sets the PDF keywords.
    *
    * @param {string} value The PDF keywords to set.
    *
    * ```typescript
    * // Load an existing PDF document
    * let document: PdfDocument = new PdfDocument(data, password);
    * // Access the document properties
    * let documentProperties: PdfDocumentInformation = document.getDocumentInformation(false);
    * // Gets the xmp metadata
    * let xmp = documentProperties.xmpMetadata;
    * // Sets keywords
    * xmp.pdfSchema.keywords = 'sample, pdf, metadata';
    * // Save the document
    * document.save('output.pdf');
    * // Destroy the document
    * document.destroy();
    * ```
    */
    keywords: string;
    /**
     * Gets the PDF version.
     *
     * @returns {string} The PDF version.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Access the document properties
     * let documentProperties: PdfDocumentInformation = document.getDocumentInformation(false);
     * // Gets the xmp metadata
     * let xmpMetadata = documentProperties.xmpMetadata;
     * // Access PDF version from PDF schema
     * let pdfVersion: string = xmpMetadata.pdfSchema.pdfVersion;
     * // Destroy the document
     * document.destroy();
     * ```
     */
    /**
    * Sets the PDF version.
    *
    * @param {string} value The PDF version to set.
    *
    * ```typescript
    * // Load an existing PDF document
    * let document: PdfDocument = new PdfDocument(data, password);
    * // Access the document properties
    * let documentProperties: PdfDocumentInformation = document.getDocumentInformation(false);
    * // Gets the xmp metadata
    * let xmp = documentProperties.xmpMetadata;
    * // Sets PDF version
    * xmp.pdfSchema.pdfVersion = '1.7';
    * // Save the document
    * document.save('output.pdf');
    * // Destroy the document
    * document.destroy();
    * ```
    */
    pdfVersion: string;
    /**
     * Gets the PDF producer.
     *
     * @returns {string} The PDF producer.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Access the document properties
     * let documentProperties: PdfDocumentInformation = document.getDocumentInformation(false);
     * // Gets the xmp metadata
     * let xmpMetadata = documentProperties.xmpMetadata;
     * // Access producer from PDF schema
     * let producer: string = xmpMetadata.pdfSchema.producer;
     * // Destroy the document
     * document.destroy();
     * ```
     */
    /**
    * Sets the PDF producer.
    *
    * @param {string} value The PDF producer to set.
    *
    * ```typescript
    * // Load an existing PDF document
    * let document: PdfDocument = new PdfDocument(data, password);
    * // Access the document properties
    * let documentProperties: PdfDocumentInformation = document.getDocumentInformation(false);
    * // Gets the xmp metadata
    * let xmp = documentProperties.xmpMetadata;
    * // Sets producer
    * xmp.pdfSchema.producer = 'Syncfusion EJ2 PDF';
    * // Save the document
    * document.save('output.pdf');
    * // Destroy the document
    * document.destroy();
    * ```
    */
    producer: string;
}