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