PdfViewerCommand CreateCommand(
    PdfViewerCommandId commandId
)

Function CreateCommand(
    commandId As PdfViewerCommandId
) As PdfViewerCommand

using DevExpress.XtraPdfViewer;
using System;
using System.Windows.Forms;

namespace ViewerCustomCommand {
    public partial class Form1 : Form {

        void ReplacePdfViewerCommandFactoryService(PdfViewer control) {
            IPdfViewerCommandFactoryService service = control.GetService<IPdfViewerCommandFactoryService>();
            if (service == null)
                return;
            control.RemoveService(typeof(IPdfViewerCommandFactoryService));
            control.AddService(typeof(IPdfViewerCommandFactoryService), new CustomPdfViewerCommandFactoryService(control,service));
        }

        public Form1() {
            InitializeComponent();
            pdfViewer1.LoadDocument("..\\..\\Demo.pdf");
            ReplacePdfViewerCommandFactoryService(pdfViewer1);
        }     
    }
}

using DevExpress.Utils;
using DevExpress.XtraPdfViewer;
using DevExpress.XtraPdfViewer.Commands;

namespace ViewerCustomCommand {
    public class CustomPdfViewerCommandFactoryService : IPdfViewerCommandFactoryService {
        readonly IPdfViewerCommandFactoryService service;
        readonly PdfViewer control;

        public CustomPdfViewerCommandFactoryService(PdfViewer control,
            IPdfViewerCommandFactoryService service) {
            Guard.ArgumentNotNull(control, "control");
            Guard.ArgumentNotNull(service, "service");
            this.control = control;
            this.service = service;
        }

        public PdfViewerCommand CreateCommand(PdfViewerCommandId id) {
            if (id == PdfViewerCommandId.NextPage)
                return new CustomNextPageCommand(control);

            return service.CreateCommand(id);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace ViewerCustomCommand {
    static class Program {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main() {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());

        }
    }
}

using DevExpress.XtraPdfViewer;
using DevExpress.XtraPdfViewer.Commands;
using System.Windows.Forms;

namespace ViewerCustomCommand {
    public class CustomNextPageCommand : PdfNextPageCommand {
        public CustomNextPageCommand(PdfViewer control)
            : base(control) {
        }

        public override void Execute() {
            MessageBox.Show("Custom command executed");
            base.Execute();
        }
    }
}

Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports System.Threading.Tasks
Imports System.Windows.Forms

Namespace ViewerCustomCommand
    Friend NotInheritable Class Program

        Private Sub New()
        End Sub

        ''' <summary>
        ''' The main entry point for the application.
        ''' </summary>
        <STAThread> _
        Shared Sub Main()
            Application.EnableVisualStyles()
            Application.SetCompatibleTextRenderingDefault(False)
            Application.Run(New Form1())

        End Sub
    End Class
End Namespace

Imports DevExpress.XtraPdfViewer
Imports DevExpress.XtraPdfViewer.Commands
Imports System.Windows.Forms

Namespace ViewerCustomCommand
    Public Class CustomNextPageCommand
        Inherits PdfNextPageCommand

        Public Sub New(ByVal control As PdfViewer)
            MyBase.New(control)
        End Sub

        Public Overrides Sub Execute()
            MessageBox.Show("Custom command executed")
            MyBase.Execute()
        End Sub
    End Class
End Namespace

Imports DevExpress.XtraPdfViewer
Imports System
Imports System.Windows.Forms

Namespace ViewerCustomCommand
    Partial Public Class Form1
        Inherits Form

        Private Sub ReplacePdfViewerCommandFactoryService(ByVal control As PdfViewer)
            Dim service As IPdfViewerCommandFactoryService = control.GetService(Of IPdfViewerCommandFactoryService)()
            If service Is Nothing Then
                Return
            End If
            control.RemoveService(GetType(IPdfViewerCommandFactoryService))
            control.AddService(GetType(IPdfViewerCommandFactoryService), New CustomPdfViewerCommandFactoryService(control,service))
        End Sub

        Public Sub New()
            InitializeComponent()
            pdfViewer1.LoadDocument("..\..\Demo.pdf")
            ReplacePdfViewerCommandFactoryService(pdfViewer1)
        End Sub
    End Class
End Namespace

Imports DevExpress.Utils
Imports DevExpress.XtraPdfViewer
Imports DevExpress.XtraPdfViewer.Commands

Namespace ViewerCustomCommand
    Public Class CustomPdfViewerCommandFactoryService
        Implements IPdfViewerCommandFactoryService

        Private ReadOnly service As IPdfViewerCommandFactoryService
        Private ReadOnly control As PdfViewer

        Public Sub New(ByVal control As PdfViewer, ByVal service As IPdfViewerCommandFactoryService)
            Guard.ArgumentNotNull(control, "control")
            Guard.ArgumentNotNull(service, "service")
            Me.control = control
            Me.service = service
        End Sub

        Public Function CreateCommand(id As PdfViewerCommandId) As PdfViewerCommand Implements IPdfViewerCommandFactoryService.CreateCommand
            If id = PdfViewerCommandId.NextPage Then
                Return New CustomNextPageCommand(control)
            End If

            Return service.CreateCommand(id)
        End Function

    End Class
End Namespace

return service.CreateCommand(id);
}

return new CustomSaveAsCommand(viewer, Rectangles);
    return service.CreateCommand(commandId);
}

If id = PdfViewerCommandId.NextPage Then Return New CustomNextPageCommand(control)
    Return service.CreateCommand(id)
End Function

If commandId = PdfViewerCommandId.SaveAsFile Then Return New CustomSaveAsCommand(viewer, Rectangles)
    Return service.CreateCommand(commandId)
End Function