Load and modify an existing PDF file

//
// 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.Text;
 
namespace DsPdfWeb.Demos
{
    // This sample loads the PDF file created by the HelloWorld sample,
    // adds a short text note to the first page, and saves the result.
    public class LoadPDF
    {
        public int CreatePDF(Stream stream)
        {
            // IMPORTANT: when working with an existing PDF file using GcPdfDocument.Load() method,
            // the stream passed to that method MUST REMAIN OPEN while working with the document.
            // This is because Load() does not load the whole PDF document into memory right away,
            // instead it loads the various parts of the PDF as needed.
            // The stream is only used for reading, and the original file itself is not modified.
            // To save the changes you need to call one of the GcPdfDocument.Save() overloads
            // as usual.
            using var fs = File.OpenRead(Path.Combine("Resources", "PDFs", "HelloWorld.pdf"));
            var doc = new GcPdfDocument();
            doc.Load(fs);
            // Add note to the (only) page in the doc:
            var page = doc.Pages.Last;
            Common.Util.AddNote(
                "This text was added to the original \"Hello World\" PDF.",
                page,
                new RectangleF(72, 72 * 3, page.Size.Width - 72 * 2, 72));
            // Done:
            doc.Save(stream);
            return doc.Pages.Count;
        }
    }
}