using System.Diagnostics;
using System.IO;
using System.Windows;
using DevExpress.Xpf.Charts;

namespace ExportToPdf {

    public partial class MainWindow : Window {
        string PDFFile = "Output.pdf";
        public MainWindow() {
            InitializeComponent();
        }

        private void Button_Click(object sender, RoutedEventArgs e) {
            PrintSizeMode sizeMode = PrintSizeMode.Stretch;
            chartControl.ExportToPdf(PDFFile, sizeMode);
            Process.Start(PDFFile);
        }
    }
}

<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:dxc="http://schemas.devexpress.com/winfx/2008/xaml/charts" x:Class="ExportToPdf.MainWindow"
        Title="MainWindow" Height="350" Width="525">
    <Grid>

        <dxc:ChartControl x:Name="chartControl">
            <dxc:ChartControl.Legend>
                <dxc:Legend/>
            </dxc:ChartControl.Legend>
            <dxc:XYDiagram2D>
                <dxc:BarSideBySideSeries2D DisplayName="Series 1">
                    <dxc:SeriesPoint Argument="A" Value="2"/>
                    <dxc:SeriesPoint Argument="B" Value="13"/>
                    <dxc:SeriesPoint Argument="C" Value="15"/>
                    <dxc:SeriesPoint Argument="D" Value="17"/>
                </dxc:BarSideBySideSeries2D>
            </dxc:XYDiagram2D>
        </dxc:ChartControl>
        <StackPanel Orientation="Horizontal">
            <Button Content="Export To PDF File" VerticalAlignment="Top" Width="120" Click="Button_Click"/>
        </StackPanel>
    </Grid>
</Window>

Imports Microsoft.VisualBasic
Imports System.Diagnostics
Imports System.IO
Imports System.Windows
Imports DevExpress.Xpf.Charts

Namespace ExportToPdf

    Partial Public Class MainWindow
        Inherits Window
        Private PDFFile As String = "Output.pdf"
        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub Button_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
            Dim sizeMode As PrintSizeMode = PrintSizeMode.Stretch
            chartControl.ExportToPdf(PDFFile, sizeMode)
            Process.Start(PDFFile)
        End Sub
    End Class
End Namespace