Introduction
This article explains a way to convert a Microsoft Word Document to PDF Format. The operation is very simple. This is used to Convert the .doc, .docx, .txt, .rtf  Document into .pdf Document.
Steps
Choose Website -> Add Reference -> .Net -> Microsoft.Office.Interop.Word 12.0.0.0 and Click on Ok.
 
Code
Namespace
using Microsoft.Office.Interop.Word;
private Microsoft.Office.Interop.Word.ApplicationClass
MSWordDoc;
object UnknownType = Type.Missing;
To Open the Word Document
MSWordDoc.Documents.Open(ref InputLocation,   
//Input File Name Location
    ref
UnknownType,    //
Conversion Conformation
    ref
UnknownType,    //
Set ReadOnly Property
    ref
UnknownType,    //
Add to the Recent Files
    ref
UnknownType,    //
Document Password Setting
    ref UnknownType,    // Password
Templete
    ref
UnknownType,    //
Revert
    ref
UnknownType,    //
Write Password to Document
    ref
UnknownType,    //
Write Password Template
    ref
UnknownType,    //
File Format
    ref
UnknownType,    //
Encoding File
    ref
UnknownType,    //
Visibility
    ref
UnknownType,    //
To Open or Repair
    ref
UnknownType,    //
Document Direction
    ref
UnknownType,    // Encoding Dialog
    ref
UnknownType);   //
XML Text Transform
                
To Get Document in PDF Format 
object SavePDFFormat = Microsoft.Office.Interop.Word.WdSaveFormat.wdFormatPDF;
To SaveAs the Document 
MSWordDoc.ActiveDocument.SaveAs(ref OutputLocation, //Output
File Location
ref SavePDFFormat,    // File Format
ref UnknownType,   
// Comment to PDF File
ref UnknownType,   
// Password
ref UnknownType,   
// Add to Recent File
ref UnknownType,   
// Write Password
ref UnknownType,   
// ReadOnly Propert
ref UnknownType,   
// Original Font Embeding
ref UnknownType,   
// Save Picture
ref UnknownType,   
// Saving Form Datas
ref UnknownType,   
// Save as AOVE Letter
ref UnknownType,   
// Encoding
ref UnknownType,   
// Inserting Line Breakes
ref UnknownType,   
// Allow Substitution
ref UnknownType,   
// Line Ending
ref UnknownType);  
// Add BiDi Marks
result
= "Success";
To Close the Document File
MSWordDoc.Documents.Close(ref UnknownType, ref
UnknownType, ref UnknownType)
To Exit the Word Application
MSWordDoc.Quit(ref UnknownType, ref
UnknownType, ref UnknownType);