public class GridDocumentExportSummaryItem :
    GridDocumentExportSummaryItemBase

@rendermode InteractiveServer
@using DevExpress.Drawing;
@inject WeatherForecastService ForecastService

<DxGrid @ref="Grid" Data="@forecasts">
    <Columns>
        <DxGridDataColumn Caption="Date" FieldName="Date" ExportWidth="500" />
        <DxGridDataColumn Caption="Temperature (C)" FieldName="TemperatureC" />
        <DxGridDataColumn Caption="Temperature (F)" FieldName="TemperatureF" />
        <DxGridDataColumn Caption="Summary" FieldName="Summary" />
    </Columns>
    <TotalSummary>
        <DxGridSummaryItem SummaryType="GridSummaryItemType.Min" FieldName="Date" />
        <DxGridSummaryItem SummaryType="GridSummaryItemType.Max" FieldName="Date" />
        <DxGridSummaryItem SummaryType="GridSummaryItemType.Min" FieldName="TemperatureC" />
        <DxGridSummaryItem SummaryType="GridSummaryItemType.Max" FieldName="TemperatureC" />
    </TotalSummary>
    <ToolbarTemplate>
        <DxToolbar>
            <DxToolbarItem Text="Export to PDF" Click="ExportPdf_Click" BeginGroup="true" />
        </DxToolbar>
    </ToolbarTemplate>
</DxGrid>

@code {
    IGrid Grid;
    private WeatherForecast[]? forecasts;

    protected override async Task OnInitializedAsync() {
        forecasts = await ForecastService.GetForecastAsync(DateOnly.FromDateTime(DateTime.Now));
    }
    async Task ExportPdf_Click() {
        await Grid.ExportToPdfAsync("ExportResult", new GridPdfExportOptions() {
            CustomizeCell = OnCustomizeCell,
        });
    }
    void OnCustomizeCell(GridDocumentExportCustomizeCellEventArgs args) {
        if (args.AreaType == DocumentExportAreaType.TotalFooter ) {
            if (args.ColumnFieldName == "Date") {
                var sum1 = args.SummaryItems[0];
                var sum2 = args.SummaryItems[1];
                args.Text = sum1.SummaryType + " " + sum1.FieldName + ": " + sum1.Value;
                args.Text += "\n" + sum2.SummaryType + " " + sum2.FieldName + ": " + sum2.Value;
            }
            if (args.ColumnFieldName == "TemperatureC") {
                args.Text = args.SummaryItems[0].Text + "°C\n" + args.SummaryItems[1].Text + "°C";
                args.ElementStyle.TextAlignment = DevExpress.XtraPrinting.TextAlignment.MiddleRight;
            }
        }
        args.Handled = true;
    }
}

using System;

public class WeatherForecast {
    public DateTime Date { get; set; }
    public int TemperatureC { get; set; }
    public string Forecast { get; set; }
    public string CloudCover { get; set; }
}

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

public class WeatherForecastService {
    private List<WeatherForecast> Forecast { get; set; }

    private static string[] CloudCover = new[] {
        "Sunny", "Partly cloudy", "Cloudy", "Storm"
    };

    Tuple<int, string>[] ConditionsForForecast = new Tuple<int, string>[] {
        Tuple.Create( 22 , "Hot"),
        Tuple.Create( 13 , "Warm"),
        Tuple.Create( 0 , "Cold"),
        Tuple.Create( -10 , "Freezing")
    };

    public WeatherForecastService() {
        Forecast = CreateForecast();
    }

    private List<WeatherForecast> CreateForecast() {
        var rng = new Random();
        DateTime startDate = DateTime.Now;
        return Enumerable.Range(1, 30).Select(index => {
            var temperatureC = rng.Next(-10, 30);
            return new WeatherForecast {
                Date = startDate.AddDays(index),
                TemperatureC = temperatureC,
                CloudCover = CloudCover[rng.Next(0, 4)],
                Forecast = ConditionsForForecast.First(c => c.Item1 <= temperatureC).Item2
            };
        }).ToList();
    }

    public List<WeatherForecast> GetForecast() {
        return Forecast;
    }

    public Task<WeatherForecast[]> GetForecastAsync(CancellationToken ct = default) {
        return Task.FromResult(Forecast.ToArray());
    }
}

// ...
builder.Services.AddSingleton<WeatherForecastService>();