How do I convert Word files to PDF programmatically?

Just wanted to add that I used Microsoft.Interop libraries, specifically ExportAsFixedFormat function which I did not see used in this thread.

using Microsoft.Office.Interop.Word;
using System.Runtime.InteropServices;
using System.IO;
using Microsoft.Office.Core;

Application app;

public string CreatePDF(string path, string exportDir)
{
    Application app = new Application();
    app.DisplayAlerts = WdAlertLevel.wdAlertsNone;
    app.Visible = true;

    var objPresSet = app.Documents;
    var objPres = objPresSet.Open(path, MsoTriState.msoTrue, MsoTriState.msoTrue, MsoTriState.msoFalse);

    var pdfFileName = Path.ChangeExtension(path, ".pdf");
    var pdfPath = Path.Combine(exportDir, pdfFileName);

    try
    {
        objPres.ExportAsFixedFormat(
            pdfPath,
            WdExportFormat.wdExportFormatPDF,
            false,
            WdExportOptimizeFor.wdExportOptimizeForPrint,
            WdExportRange.wdExportAllDocument
        );
    }
    catch
    {
        pdfPath = null;
    }
    finally
    {
        objPres.Close();
    }
    return pdfPath;
}

Use a foreach loop instead of a for loop - it solved my problem.

int j = 0;
foreach (Microsoft.Office.Interop.Word.Page p in pane.Pages)
{
    var bits = p.EnhMetaFileBits;
    var target = path1 +j.ToString()+  "_image.doc";
    try
    {
        using (var ms = new MemoryStream((byte[])(bits)))
        {
            var image = System.Drawing.Image.FromStream(ms);
            var pngTarget = Path.ChangeExtension(target, "png");
            image.Save(pngTarget, System.Drawing.Imaging.ImageFormat.Png);
        }
    }
    catch (System.Exception ex)
    {
        MessageBox.Show(ex.Message);  
    }
    j++;
}

Here is a modification of a program that worked for me. It uses Word 2007 with the Save As PDF add-in installed. It searches a directory for .doc files, opens them in Word and then saves them as a PDF. Note that you'll need to add a reference to Microsoft.Office.Interop.Word to the solution.

using Microsoft.Office.Interop.Word;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;

...

// Create a new Microsoft Word application object
Microsoft.Office.Interop.Word.Application word = new Microsoft.Office.Interop.Word.Application();

// C# doesn't have optional arguments so we'll need a dummy value
object oMissing = System.Reflection.Missing.Value;

// Get list of Word files in specified directory
DirectoryInfo dirInfo = new DirectoryInfo(@"\\server\folder");
FileInfo[] wordFiles = dirInfo.GetFiles("*.doc");

word.Visible = false;
word.ScreenUpdating = false;

foreach (FileInfo wordFile in wordFiles)
{
    // Cast as Object for word Open method
    Object filename = (Object)wordFile.FullName;

    // Use the dummy value as a placeholder for optional arguments
    Document doc = word.Documents.Open(ref filename, ref oMissing,
        ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing,
        ref oMissing, ref oMissing, ref oMissing, ref oMissing, ref oMissing,
        ref oMissing, ref oMissing, ref oMissing, ref oMissing);
    doc.Activate();

    object outputFileName = wordFile.FullName.Replace(".doc", ".pdf");
    object fileFormat = WdSaveFormat.wdFormatPDF;

    // Save document into PDF Format
    doc.SaveAs(ref outputFileName,
        ref fileFormat, ref oMissing, ref oMissing,
        ref oMissing, ref oMissing, ref oMissing, ref oMissing,
        ref oMissing, ref oMissing, ref oMissing, ref oMissing,
        ref oMissing, ref oMissing, ref oMissing, ref oMissing);

    // Close the Word document, but leave the Word application open.
    // doc has to be cast to type _Document so that it will find the
    // correct Close method.                
    object saveChanges = WdSaveOptions.wdDoNotSaveChanges;
    ((_Document)doc).Close(ref saveChanges, ref oMissing, ref oMissing);
    doc = null;
}

// word has to be cast to type _Application so that it will find
// the correct Quit method.
((_Application)word).Quit(ref oMissing, ref oMissing, ref oMissing);
word = null;

To sum it up for vb.net users, the free option (must have office installed):

Microsoft office assembies download:

• pia for office 2010

• pia for office 2007

• Add reference to Microsoft.Office.Interop.Word.Application

• Add using or import (vb.net) statement to Microsoft.Office.Interop.Word.Application

VB.NET example:

        Dim word As Application = New Application()
        Dim doc As Document = word.Documents.Open("c:\document.docx")
        doc.Activate()
        doc.SaveAs2("c:\document.pdf", WdSaveFormat.wdFormatPDF)
        doc.Close()