How to read from pdf file?

Question

I am new to reading pdf using C# where I have below function in my project. How to recognize text position in pdf file?
Here _dblRect has 151.0, 696.0, 400.0, 500.0
_strFileName is txt file name.
Can someone explain how this function works?
private string fcnTextFromCrop(string _strFileName, double[] _dblRect, CAcroPDDoc _docOriginal, int _intPage)
            string str = "";
            try
                object jSObject = _docOriginal.GetJSObject();
                System.Type type = jSObject.GetType();
                object target = null;
                object[] args = new object[] { _intPage };
                target = type.InvokeMember("extractPages", BindingFlags.InvokeMethod | BindingFlags.Public | BindingFlags.Instance, null, jSObject, args);
                object[] objArray2 = new object[] { "Crop", 0, 0, _dblRect };
                type.InvokeMember("setPageBoxes", BindingFlags.InvokeMethod | BindingFlags.Public | BindingFlags.Instance, null, target, objArray2);
                object[] objArray3 = new object[] { _strFileName, "com.adobe.acrobat.plain-text" };
                type.InvokeMember("saveAs", BindingFlags.InvokeMethod | BindingFlags.Public | BindingFlags.Instance, null, target, objArray3);
                object[] objArray4 = new object[] { true };
                type.InvokeMember("closeDoc", BindingFlags.InvokeMethod | BindingFlags.Public | BindingFlags.Instance, null, target, objArray4);
                using (StreamReader reader = new StreamReader(_strFileName))
                    str = reader.ReadToEnd();
                    reader.Close();
                System.IO.File.Delete(_strFileName);
            catch
                str = "";
            return str;

Answer 1

Without reading it in detail, this seems to be automating a save as text function in Acrobat. This will not give you any position information.
If you want position information without writing a plug-in, you need to use the getPageNthWord and getPageNthWordQuads methods in JavaScript.
If you have not already done so, you will need to download the Acrobat SDK which has the documentation you need.
Writing in C# makes even very simple things complicated; if you have a choice, consider VB.