I have worked on the same requirement and I am able to achieve this by the following steps.
Step1: Locating Source Pdf File and Destination file Path
Step2: Read Source Pdf file and Searching for the location of string that we want to replace
Step3: Replacing the string with new one.
using iTextSharp.text;
using iTextSharp.text.pdf;
using iTextSharp.text.pdf.parser;
using PDFExtraction;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace PDFReplaceTextUsingItextSharp
{
public partial class ExtractPdf : System.Web.UI.Page
{
static iTextSharp.text.pdf.PdfStamper stamper = null;
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Replace_Click(object sender, EventArgs e)
{
string ReplacingVariable = txtReplace.Text;
string sourceFile = "Source File Path";
string descFile = "Destination File Path";
PdfReader pReader = new PdfReader(sourceFile);
stamper = new iTextSharp.text.pdf.PdfStamper(pReader, new System.IO.FileStream(descFile, System.IO.FileMode.Create));
PDFTextGetter("ExistingVariableinPDF", ReplacingVariable , StringComparison.CurrentCultureIgnoreCase, sourceFile, descFile);
stamper.Close();
pReader.Close();
}
/// <summary>
/// This method is used to search for the location words in pdf and update it with the words given from replacingText variable
/// </summary>
/// <param name="pSearch">Searchable String</param>
/// <param name="replacingText">Replacing String</param>
/// <param name="SC">Case Ignorance</param>
/// <param name="SourceFile">Path of the source file</param>
/// <param name="DestinationFile">Path of the destination file</param>
public static void PDFTextGetter(string pSearch, string replacingText, StringComparison SC, string SourceFile, string DestinationFile)
{
try
{
iTextSharp.text.pdf.PdfContentByte cb = null;
iTextSharp.text.pdf.PdfContentByte cb2 = null;
iTextSharp.text.pdf.PdfWriter writer = null;
iTextSharp.text.pdf.BaseFont bf = null;
if (System.IO.File.Exists(SourceFile))
{
PdfReader pReader = new PdfReader(SourceFile);
for (int page = 1; page <= pReader.NumberOfPages; page++)
{
myLocationTextExtractionStrategy strategy = new myLocationTextExtractionStrategy();
cb = stamper.GetOverContent(page);
cb2 = stamper.GetOverContent(page);
//Send some data contained in PdfContentByte, looks like the first is always cero for me and the second 100,
//but i'm not sure if this could change in some cases
strategy.UndercontentCharacterSpacing = (int)cb.CharacterSpacing;
strategy.UndercontentHorizontalScaling = (int)cb.HorizontalScaling;
//It's not really needed to get the text back, but we have to call this line ALWAYS,
//because it triggers the process that will get all chunks from PDF into our strategy Object
string currentText = PdfTextExtractor.GetTextFromPage(pReader, page, strategy);
//The real getter process starts in the following line
List<iTextSharp.text.Rectangle> MatchesFound = strategy.GetTextLocations(pSearch, SC);
//Set the fill color of the shapes, I don't use a border because it would make the rect bigger
//but maybe using a thin border could be a solution if you see the currect rect is not big enough to cover all the text it should cover
cb.SetColorFill(BaseColor.WHITE);
//MatchesFound contains all text with locations, so do whatever you want with it, this highlights them using PINK color:
foreach (iTextSharp.text.Rectangle rect in MatchesFound)
{
//width
cb.Rectangle(rect.Left, rect.Bottom, 60, rect.Height);
cb.Fill();
cb2.SetColorFill(BaseColor.BLACK);
bf = BaseFont.CreateFont(BaseFont.HELVETICA_BOLD, BaseFont.CP1252, BaseFont.NOT_EMBEDDED);
cb2.SetFontAndSize(bf, 9);
cb2.BeginText();
cb2.ShowTextAligned(0, replacingText, rect.Left, rect.Bottom, 0);
cb2.EndText();
cb2.Fill();
}
}
}
}
catch (Exception ex)
{
}
}
}
}
