// using System.Diagnostics;
string source_file_dir = project.Directory;
string source_file_name = "test.pdf";
string source_file_path = source_file_dir + "\\" + source_file_name;
string result_file_path = source_file_path.Replace(".pdf", ".xml");
System.Diagnostics.Process p = new System.Diagnostics.Process();
p.StartInfo.UseShellExecute = false;
p.StartInfo.CreateNoWindow = true;
p.StartInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
p.StartInfo.FileName =@"C:\Program Files\CoolUtils\Total PDF Converter\PDFConverter64.exe"; // Путь к программе
p.StartInfo.Arguments = source_file_path + " " + result_file_path + @" -c XML";
project.Variables["args"].Value = p.StartInfo.Arguments;
p.Start();
p.WaitForExit(99999);