PdfCreatorObj.PrintFile isn't sending the job to jobqueue

I am implementing COM interface in C#.
I have initiated JobQueue and called pdfCreatorObj.PrintFile(filepath). After this, the job didn’t reach the jobqueue.

Following is the code snippet:

if (pdfCreator.IsInstanceRunning)

  // Wait till doc gets queued up.
        while (jobQueue.Count != 1)
           if (starttime.AddSeconds(timeout) < DateTime.Now)
                WriteToLog("", "Loading document timedout", LogLevel.ERROR );
                 throw new Exception ("Failed to load the document:"+srcFileFullName +" 
                     for printing");

        PrintJob printJob = jobQueue.NextJob;


From the above code I am always getting the exception: “Failed to load the document”