Merge two PDFs into a single document

//
// This code is part of Document Solutions for PDF demos.
// Copyright (c) MESCIUS inc. All rights reserved.
//
using System;
using System.IO;
using System.Drawing;
using GrapeCity.Documents.Pdf;
using GrapeCity.Documents.Pdf.Annotations;
 
namespace DsPdfWeb.Demos
{
    // This sample shows how to merge two existing PDFs into a single document.
    // The method GcPdfDocument.MergeWithDocument() provides this feature,
    // and allows inserting all or some pages from another PDF into the current
    // document. The simplest form of this method is demonstrated in this sample,
    // appending a whole PDF to the current document.
    public class MergePDFs
    {
        public int CreatePDF(Stream stream)
        {
            using var fs0 = File.OpenRead(Path.Combine("Resources", "PDFs", "The-Rich-History-of-JavaScript.pdf"));
            using var fs1 = File.OpenRead(Path.Combine("Resources", "PDFs", "CompleteJavaScriptBook.pdf"));
 
            var doc = new GcPdfDocument();
            doc.Load(fs0);
            // Save page count for the navigation link added below:
            var pgNo = doc.Pages.Count;
            var doc1 = new GcPdfDocument();
            doc1.Load(fs1);
            doc.MergeWithDocument(doc1, new MergeDocumentOptions());
 
            // Insert a note at the beginning of the document:
            var page = doc.Pages.Insert(0);
            var rc = Common.Util.AddNote(
                "GcPdfDocument.MergeWithDocument() method allows adding to the current document all or some pages " +
                "from another document.\n" +
                "In this sample we load one PDF, append another whole PDF to it, and save the result.\n" +
                "Click this note to jump directly to the first page of the 2nd document.",
                page);
 
            // Link the note to the first page of the second document:
            page.Annotations.Add(new LinkAnnotation(rc, new DestinationFit(pgNo + 1)));
            // Done (target document must be saved BEFORE the source is disposed):
            doc.Save(stream);
            return doc.Pages.Count;
        }
    }
}