The following example show you how to set the cell’s border width and color attributes. We can set the width and color at once using the setBorderWidth() and setBorderColor(). Or you can set it individually for each side of the cell’s border. You can also set the background color of a cell using the setBackgroundColor() method.

package org.kodejava.itextpdf;

import com.itextpdf.text.BaseColor;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Phrase;
import com.itextpdf.text.pdf.PdfPCell;
import com.itextpdf.text.pdf.PdfPTable;
import com.itextpdf.text.pdf.PdfWriter;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;

public class TableCellBorderDemo {
    public static void main(String[] args) {
        Document doc = new Document();
        try {
            PdfWriter.getInstance(doc, new FileOutputStream("TableCellBorder.pdf"));
            doc.open();

            PdfPTable table = new PdfPTable(3);
            PdfPCell cell1 = new PdfPCell(new Phrase("Cell 1"));
            cell1.setUseBorderPadding(true);

            // Setting cell's border width and color
            cell1.setBorderWidth(5f);
            cell1.setBorderColor(BaseColor.BLUE);
            table.addCell(cell1);

            PdfPCell cell2 = new PdfPCell(new Phrase("Cell 2"));
            cell2.setUseBorderPadding(true);

            // Setting cell's background color
            cell2.setBackgroundColor(BaseColor.GRAY);

            // Setting cell's individual border color
            cell2.setBorderWidthTop(1f);
            cell2.setBorderColorTop(BaseColor.RED);
            cell2.setBorderColorRight(BaseColor.GREEN);
            cell2.setBorderColorBottom(BaseColor.BLUE);
            cell2.setBorderColorLeft(BaseColor.BLACK);
            table.addCell(cell2);

            PdfPCell cell3 = new PdfPCell(new Phrase("Cell 3"));
            cell3.setUseBorderPadding(true);

            // Setting cell's individual border width
            cell3.setBorderWidthTop(2f);
            cell3.setBorderWidthRight(1f);
            cell3.setBorderWidthBottom(2f);
            cell3.setBorderWidthLeft(1f);
            table.addCell(cell3);
            table.completeRow();

            doc.add(table);
        } catch (DocumentException | FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            doc.close();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itextpdf</artifactId>
    <version>5.5.13.3</version>
</dependency>