C#

You can't 'parse' an existing PDF file using iText, you can only 'read' it page per page.
What does this mean?
The pdf format is just a canvas where text and graphics are placed without any structure information. As such there aren't any 'iText-objects' in a PDF file. In each page there will probably be a number of 'Strings', but you can't reconstruct a phrase or a paragraph using these strings. There are probably a number of lines drawn, but you can't retrieve a Table-object based on these lines. In short: parsing the content of a PDF-file is NOT POSSIBLE with iText. Post your question on the newsgroup news://comp.text.pdf and maybe you will get some answers from people that have built tools that can parse PDF and extract some of its contents, but don't expect tools that will perform a bullet-proof conversion to structured text.

What iText DOES provide is the possibility to READ a PDF document and copy an entire page of this file into the PDF file you are constructing from scratch. This can be useful if you want to create a new document based on (an) existing document(s). You can add a Watermark, pagenumbers,...

using System;
using System.Runtime.InteropServices;
 
[assembly: ComVisible(true)]
[assembly: Guid("519a4822-f224-47fa-bdc7-8037829365dc")]
 
[InterfaceType(ComInterfaceType.InterfaceIsDual)]
[Guid("f9b77b61-b4f0-4be4-9c53-ded9592e90c6")]
public interface ITest
{
  [DispId(0)]
  int Foo(string value);
}
 
[ClassInterface(ClassInterfaceType.None)]
[Guid("ae5e53c8-54d6-4667-9396-582f5c8611bf")]
public class Test
{
  public int Foo(string value)
  {
    return value.Length;
  }
}

csc.exe /t:library test.cs

regasm.exe /tlb test.dll

oleview.exe test.tlb

// Generated .IDL file (by the OLE/COM Object Viewer)
// 
// typelib filename: test.tlb
 
[
  uuid(519A4822-F224-47FA-BDC7-8037829365DC),
  version(1.0),
  custom(90883F05-3D28-11D2-8F17-00A0C9A6186D, Test, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null)
 
]
library Test
{
    // TLib :     // TLib : mscorlib.dll : {BED7F4EA-1A96-11D2-8F08-00A0C9A6186D}
    importlib("mscorlib.tlb");
    // TLib : OLE Automation : {00020430-0000-0000-C000-000000000046}
    importlib("stdole2.tlb");
 
    // Forward declare all types defined in this typelib
    interface ITest;
 
    [
      odl,
      uuid(F9B77B61-B4F0-4BE4-9C53-DED9592E90C6),
      version(1.0),
      dual,
      oleautomation,
      custom(0F21F359-AB84-41E8-9A78-36D110E6D2F9, ITest)    
 
    ]
    interface ITest : IDispatch {
        [id(00000000), propget,
          custom(54FC8F55-38DE-4703-9C4E-250351302B1C, 1)]
        HRESULT Foo(
                        [in] BSTR value, 
                        [out, retval] long* pRetVal);
    };
 
    [
      uuid(AE5E53C8-54D6-4667-9396-582F5C8611BF),
      version(1.0),
      custom(0F21F359-AB84-41E8-9A78-36D110E6D2F9, Test)
    ]
    coclass Test {
        [default] interface _Object;
    };
};

Memory Leak Issues

Passing the address of an initialized CComBSTR to a function as an [out] parameter causes a memory leak.

In the example below, the string allocated to hold the string "Initialized" is leaked when the function OutString replaces the string.

CComBSTR bstrLeak(L"Initialized");
HRESULT hr = OutString(&bstrLeak);

To avoid the leak, call the Empty method on existing CComBSTR objects before passing the address as an [out] parameter.

Note that the same code would not cause a leak if the function's parameter was [in, out].