Add text to the existing PDF document using ByteScout PDF SDK
In this example ByteScout PDF SDK is used to add text to the first page of the existing PDF document (HelloWorld.pdf) and save new document as HelloWorldAgain.pdf

Source PDF document which is taken as source to modify (add text) and save as new document file
PDF document with text added to the first page

Program.vb:
VB

'*******************************************************************
'       ByteScout PDF SDK
'                                                                   
'       Copyright © 2016 Bytescout, http://www.bytescout.com        
'       ALL RIGHTS RESERVED                                         
'                                                                   
'*******************************************************************

Imports Bytescout.PDF

''' <summary>
''' This example demonstrates how to load and modify an existing document.
''' </summary>
Class Program

    Shared Sub Main()

        ' Create new Document object
        Dim pdfDocument = New Document()
        pdfDocument.RegistrationName = "demo"
		pdfDocument.RegistrationKey = "demo"

        '  Load existing document
        pdfDocument.Load("sample.pdf")

        ' Add new page to loaded document
        Dim page As New Page(PaperFormat.A4)
        Dim font As New Font(StandardFonts.Times, 24)
        Dim brush As New SolidBrush()
        page.Canvas.DrawString("New Page", font, brush, 20, 20)
        pdfDocument.Pages.Add(page)

        ' Save document to file
        pdfDocument.Save("result.pdf")

        ' Cleanup 
		pdfDocument.Dispose()

        ' Open document in default PDF viewer app
        Process.Start("result.pdf")

    End Sub

End Class 

Program.cs:
C#

//*******************************************************************
//       ByteScout PDF SDK		                                     
//                                                                   
//       Copyright © 2016 ByteScout - http://www.bytescout.com       
//       ALL RIGHTS RESERVED                                         
//                                                                   
//*******************************************************************

using System.Diagnostics;
using Bytescout.PDF;

namespace LoadDocument
{
	/// <summary>
	/// This example demonstrates how to load and modify an existing document.
	/// </summary>
	class Program
	{
		static void Main()
		{
			// Create new Document object
			Document pdfDocument = new Document();
			pdfDocument.RegistrationName = "demo";
			pdfDocument.RegistrationKey = "demo";
			
			// Load existing document
			pdfDocument.Load("sample.pdf");
			
			// Add new page to loaded document
			Page page = new Page(PaperFormat.A4);
			Font font = new Font(StandardFonts.Times, 24);
			Brush brush = new SolidBrush();
			page.Canvas.DrawString("New Page", font, brush, 20, 20);
			pdfDocument.Pages.Add(page);
			
			// Save document to file
			pdfDocument.Save("result.pdf");

			// Cleanup 
			pdfDocument.Dispose();

			// Open document in default PDF viewer app
			Process.Start("result.pdf");
		}
	}
}