using iTextSharp.text.pdf;
using iTextSharp.text.pdf.parser;
using System.IO;


public string ReadPdfFile(string fileName)
{
StringBuilder text = new StringBuilder();


if (File.Exists(fileName))
{
PdfReader pdfReader = new PdfReader(fileName);


for (int page = 1; page <= pdfReader.NumberOfPages; page++)
{
ITextExtractionStrategy strategy = new SimpleTextExtractionStrategy();
string currentText = PdfTextExtractor.GetTextFromPage(pdfReader, page, strategy);


currentText = Encoding.UTF8.GetString(ASCIIEncoding.Convert(Encoding.Default, Encoding.UTF8, Encoding.Default.GetBytes(currentText)));
text.Append(currentText);
}
pdfReader.Close();
}
return text.ToString();
}

Here is a VB.NET solution based on ShravankumarKumar's solution.

This will ONLY give you the text. The images are a different story.

Public Shared Function GetTextFromPDF(PdfFileName As String) As String
Dim oReader As New iTextSharp.text.pdf.PdfReader(PdfFileName)


Dim sOut = ""


For i = 1 To oReader.NumberOfPages
Dim its As New iTextSharp.text.pdf.parser.SimpleTextExtractionStrategy


sOut &= iTextSharp.text.pdf.parser.PdfTextExtractor.GetTextFromPage(oReader, i, its)
Next


Return sOut
End Function

Public Sub PDFTxtToPdf(ByVal sTxtfile As String, ByVal sPDFSourcefile As String)
Dim sr As StreamReader = New StreamReader(sTxtfile)
Dim doc As New Document()
PdfWriter.GetInstance(doc, New FileStream(sPDFSourcefile, FileMode.Create))
doc.Open()
doc.Add(New Paragraph(sr.ReadToEnd()))
doc.Close()
End Sub

LGPL / FOSS iTextSharp 4.x

var pdfReader = new PdfReader(path); //other filestream etc
byte[] pageContent = _pdfReader .GetPageContent(pageNum); //not zero based
byte[] utf8 = Encoding.Convert(Encoding.Default, Encoding.UTF8, pageContent);
string textFromPage = Encoding.UTF8.GetString(utf8);

None of the other answers were useful to me, they all seem to target the AGPL v5 of iTextSharp. I could never find any reference to SimpleTextExtractionStrategy or LocationTextExtractionStrategy in the FOSS version.

Something else that might be very useful in conjunction with this:

const string PdfTableFormat = @"\(.*\)Tj";
Regex PdfTableRegex = new Regex(PdfTableFormat, RegexOptions.Compiled);


List<string> ExtractPdfContent(string rawPdfContent)
{
var matches = PdfTableRegex.Matches(rawPdfContent);


var list = matches.Cast<Match>()
.Select(m => m.Value
.Substring(1) //remove leading (
.Remove(m.Value.Length - 4) //remove trailing )Tj
.Replace(@"\)", ")") //unencode parens
.Replace(@"\(", "(")
.Trim()
)
.ToList();
return list;
}

This will extract the text-only data from the PDF if the text displayed is Foo(bar) it will be encoded in the PDF as (Foo\(bar\))Tj, this method would return Foo(bar) as expected. This method will strip out lots of additional information such as location coordinates from the raw pdf content.

In my case, I just wanted the text from a specific area of the PDF document so I used a rectangle around the area and extracted the text from it. In the sample below the coordinates are for the entire page. I don't have PDF authoring tools so when it came time to narrow down the rectangle to the specific location I took a few guesses at the coordinates until the area was found.

Rectangle _pdfRect = new Rectangle(0f, 0f, 612f, 792f); // Entire page - PDF coordinate system 0,0 is bottom left corner.  72 points / inch
RenderFilter _renderfilter = new RegionTextRenderFilter(_pdfRect);
ITextExtractionStrategy _strategy = new FilteredTextRenderListener(new LocationTextExtractionStrategy(), _filter);
string _text = PdfTextExtractor.GetTextFromPage(_pdfReader, 1, _strategy);

As noted by the above comments the resulting text doesn't maintain any of the formatting found in the PDF document, however, I was happy that it did preserve the carriage returns. In my case, there were enough constants in the text that I was able to extract the values that I required.

Here an improved answer of ShravankumarKumar. I created special classes for the pages so you can access words in the pdf based on the text rows and the word in that row.

using iTextSharp.text.pdf;
using iTextSharp.text.pdf.parser;


//create a list of pdf pages
var pages = new List<PdfPage>();


//load the pdf into the reader. NOTE: path can also be replaced with a byte array
using (PdfReader reader = new PdfReader(path))
{
//loop all the pages and extract the text
for (int i = 1; i <= reader.NumberOfPages; i++)
{
pages.Add(new PdfPage()
{
content = PdfTextExtractor.GetTextFromPage(reader, i)
});
}
}


//use linq to create the rows and words by splitting on newline and space
pages.ForEach(x => x.rows = x.content.Split('\n').Select(y =>
new PdfRow() {
content = y,
words = y.Split(' ').ToList()
}
).ToList());

The custom classes

class PdfPage
{
public string content { get; set; }
public List<PdfRow> rows { get; set; }
}




class PdfRow
{
public string content { get; set; }
public List<string> words { get; set; }
}

Now you can get a word by row and word index.

string myWord = pages[0].rows[12].words[4];

Or use Linq to find the rows containing a specific word.

//find the rows in a specific page containing a word
var myRows = pages[0].rows.Where(x => x.words.Any(y => y == "myWord1")).ToList();


//find the rows in all pages containing a word
var myRows = pages.SelectMany(r => r.rows).Where(x => x.words.Any(y => y == "myWord2")).ToList();