This is a simple code to convert any Word document to a PDF using the Word interop.

using Word = Microsoft.Office.Interop.Word;

...

public Word.Document wordDocument { get; set; }

public void ConvertWord2PDF()
{
    var appWord = new Word.Application();
    wordDocument = appWord.Documents.Open(@"D:\Tests\test.docx");
    wordDocument.ExportAsFixedFormat(@"D:\Tests\test.pdf", Word.WdExportFormat.wdExportFormatPDF);
}