Long time ago I have written blog to rename column name. 

using System.ComponentModel;

namespace PdfReportSamples.Models
{
    public enum JobTitle
    {
        [Description("Grunt")]
        Grunt,

        [Description("Programmer")]
        Programmer,

        [Description("Analyst Programmer")]
        AnalystProgrammer,

        [Description("Project Manager")]
        ProjectManager,

        [Description("Chief Information Officer")]
        ChiefInformationOfficer,
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using PdfReportSamples.Models;
using PdfRpt.Aggregates.Numbers;
using PdfRpt.ColumnsItemsTemplates;
using PdfRpt.Core.Contracts;
using PdfRpt.Core.Helper;
using PdfRpt.DataAnnotations;

namespace PdfReportSamples.DataAnnotations
{
    public class Person
    {
        [IsVisible(false)]
        public int Id { get; set; }

        [DisplayName("User name")]
        //Note: If you don't specify the ColumnItemsTemplate, a new TextBlockField() will be used automatically.
        [ColumnItemsTemplate(typeof(TextBlockField))]
        public string Name { get; set; }

        [DisplayName("Job title")]
        public JobTitle JobTitle { set; get; }

        [DisplayName("Date of birth")]
        [DisplayFormat(DataFormatString = "{0:MM/dd/yyyy}")]
        public DateTime DateOfBirth { get; set; }

        [DisplayName("Date of death")]
        [DisplayFormat(NullDisplayText = "-", DataFormatString = "{0:MM/dd/yyyy}")]
        public DateTime? DateOfDeath { get; set; }

        [DisplayFormat(DataFormatString = "{0:n0}")]
        [CustomAggregateFunction(typeof(Sum))]
        public int Salary { get; set; }

        [IsCalculatedField(true)]
        [DisplayName("Calculated Field")]
        [DisplayFormat(DataFormatString = "{0:n0}")]
        [AggregateFunction(AggregateFunction.Sum)]
        public string CalculatedField { get; set; }

        [CalculatedFieldFormula("CalculatedField")]
        public static Func<IList<CellData>, object> CalculatedFieldFormula =
                                                    list =>
                                                    {
                                                        if (list == null) return string.Empty;
                                                        var salary = (int)list.GetValueOf<Person>(x => x.Salary);
                                                        return salary * 0.8;
                                                    };//Note: It's a static field, not a property.
    }
}

using System;
using System.Collections.Generic;
using PdfReportSamples.Models;

namespace PdfReportSamples.DataAnnotations
{
    public static class PersonnelDataSource
    {
        public static IList<Person> CreatePersonnelList()
        {
            return new List<Person>
            {
                new Person
                {
                    Id = 1,
                    Name = "Edward",
                    DateOfBirth = new DateTime(1900, 1, 1),
                    DateOfDeath = new DateTime(1990, 10, 15),
                    JobTitle = JobTitle.ChiefInformationOfficer,
                    Salary = 5000
                },
                new Person
                {
                    Id = 2,
                    Name = "Margaret", 
                    DateOfBirth = new DateTime(1950, 2, 9), 
                    DateOfDeath = null,
                    JobTitle = JobTitle.AnalystProgrammer,
                    Salary = 4000
                },
                new Person
                {
                    Id = 3,
                    Name = "Grant", 
                    DateOfBirth = new DateTime(1975, 6, 13), 
                    DateOfDeath = null,
                    JobTitle = JobTitle.Programmer,
                    Salary = 3500
                }
            };
        }
    }
}

using System;
using PdfRpt.Core.Contracts;
using PdfRpt.FluentInterface;

namespace PdfReportSamples.DataAnnotations
{
    public class DataAnnotationsPdfReport
    {
        public IPdfReportData CreatePdfReport()
        {
            return new PdfReport().DocumentPreferences(doc =>
            {
                doc.RunDirection(PdfRunDirection.LeftToRight);
                doc.Orientation(PageOrientation.Portrait);
                doc.PageSize(PdfPageSize.A4);
                doc.DocumentMetadata(new DocumentMetadata { Author = "Vahid", Application = "PdfRpt", Keywords = "Test", Subject = "Test Rpt", Title = "Test" });
            })
             .DefaultFonts(fonts =>
             {
                 fonts.Path(Environment.GetEnvironmentVariable("SystemRoot") + "\\fonts\\tahoma.ttf",
                                  Environment.GetEnvironmentVariable("SystemRoot") + "\\fonts\\verdana.ttf");
             })
             .PagesFooter(footer =>
             {
                 footer.DefaultFooter(printDate: DateTime.Now.ToString("MM/dd/yyyy"));
             })
             .PagesHeader(header =>
             {
                 header.DefaultHeader(defaultHeader =>
                 {
                     defaultHeader.ImagePath(AppPath.ApplicationPath + "\\Images\\01.png");
                     defaultHeader.Message("new rpt.");
                     defaultHeader.RunDirection(PdfRunDirection.LeftToRight);
                 });
             })
             .MainTableTemplate(template =>
             {
                 template.BasicTemplate(BasicTemplate.ClassicTemplate);
             })
             .MainTablePreferences(table =>
             {
                 table.ColumnsWidthsType(TableColumnWidthType.FitToContent);
             })
             .MainTableDataSource(dataSource =>
             {
                 dataSource.StronglyTypedList(PersonnelDataSource.CreatePersonnelList());
             })
             .MainTableEvents(events =>
             {
                 events.DataSourceIsEmpty(message: "There is no data available to display.");
             })
             .MainTableSummarySettings(summary =>
             {
                 summary.OverallSummarySettings("Total");
                 summary.PageSummarySettings("Page Summary");
                 summary.PreviousPageSummarySettings("Pervious Page Summary");
             })
             .MainTableAdHocColumnsConventions(adHocColumns =>
             {
                 adHocColumns.ShowRowNumberColumn(true);
                 adHocColumns.RowNumberColumnCaption("#");
             })
             .Export(export =>
             {
                 export.ToExcel();
                 export.ToXml();
             })
             .Generate(data => data.AsPdfFile(AppPath.ApplicationPath + "\\Pdf\\DataAnnotationsSampleRpt.pdf"));
        }
    }
}

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
        <RowDefinition Height="*" />
        <RowDefinition Height="28" />
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="200" />
    </Grid.ColumnDefinitions>
</Grid>

 <ColumnDefinition Width="69*" />   <!-- Take 69% of remainder -->
    <ColumnDefinition Width="31*"/> <!-- Take 31% of remainder -->

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
        <RowDefinition Height="*" />
        <RowDefinition Height="28" />
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="200" />
    </Grid.ColumnDefinitions>
    <Label Grid.Row="0" Grid.Column="0" Content="Name:"/>
    <Label Grid.Row="1" Grid.Column="0" Content="E-Mail:"/>
    <Label Grid.Row="2" Grid.Column="0" Content="Comment:"/>
    <TextBox Grid.Column="1" Grid.Row="0" Margin="3" />
    <TextBox Grid.Column="1" Grid.Row="1" Margin="3" />
    <TextBox Grid.Column="1" Grid.Row="2" Margin="3" />
    <Button Grid.Column="1" Grid.Row="3" HorizontalAlignment="Right" 
            MinWidth="80" Margin="3" Content="Send"  />
</Grid>

Auto sized GridLength.Auto
Star sized new GridLength(1,GridUnitType.Star)
Fixed size new GridLength(100,GridUnitType.Pixel)

Grid grid = new Grid();
 
ColumnDefinition col1 = new ColumnDefinition();
col1.Width = GridLength.Auto;
ColumnDefinition col2 = new ColumnDefinition();
col2.Width = new GridLength(1,GridUnitType.Star);
 
grid.ColumnDefinitions.Add(col1);
grid.ColumnDefinitions.Add(col2);

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="Auto"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Label Content="Left" Grid.Column="0" />
    <GridSplitter HorizontalAlignment="Right" 
                  VerticalAlignment="Stretch" 
                  Grid.Column="1" ResizeBehavior="PreviousAndNext"
                  Width="5" Background="#FFBCBCBC"/>
    <Label Content="Right" Grid.Column="2" />
</Grid>

 var m = new ITModel.ITModelContainer();
        var list = (from pp in m.PERSONNELs
                    select pp).ToList();

        string pdfpath = Server.MapPath("PDFs");
        using (var pdfDoc = new Document(PageSize.A4))
        {
            var pdfWriter = PdfWriter.GetInstance(pdfDoc, new FileStream(pdfpath + "/Personnel2.pdf", FileMode.Create));
            pdfDoc.Open();
            var fontPath = Environment.GetEnvironmentVariable("SystemRoot") + "\\fonts\\tahoma.ttf";
            var baseFont = BaseFont.CreateFont(fontPath, BaseFont.IDENTITY_H, BaseFont.EMBEDDED);
            var tahomaFont = new Font(baseFont, 10, Font.NORMAL, BaseColor.BLACK);
            float[] widths = new float[] { 1f, 2f };

            PdfPTable table = new PdfPTable(2)
                {
                    TotalWidth = 216f,
                    LockedWidth = true,
                    HorizontalAlignment = 0,
                    SpacingBefore = 20f,
                    SpacingAfter = 30f
                };

            table.SetWidths(widths);
            PdfPCell cell = new PdfPCell(new Phrase("لیست پرسنل", tahomaFont)) { RunDirection = PdfWriter.RUN_DIRECTION_RTL, Colspan = 2, Border = 0, HorizontalAlignment = 1 };

            table.AddCell(cell);
            foreach (var item in list)
            {
                PdfPCell cell2 = new PdfPCell(new Phrase(item.PERSON_ID.ToString(), tahomaFont)) { RunDirection = PdfWriter.RUN_DIRECTION_RTL };
                PdfPCell cell3 = new PdfPCell(new Phrase(item.FIRST_NAME + " " + item.LAST_NAME, tahomaFont)) { RunDirection = PdfWriter.RUN_DIRECTION_RTL };
                table.AddCell(cell2);
                table.AddCell(cell3);
            }
            pdfDoc.Add(table);
        }

{ RunDirection = PdfWriter.RUN_DIRECTION_RTL };