PDFCreator 4.1.2 - Error adding attachment

Dear alls,

Environment: PDFCreator (version 4.1.2 on Windows 7) through COM interface.
Goal: Print xls sheet to pdf file using an existing pdf file as attachment.

Calling method PrintJob.ConvertTo(String path), I get the following error : "Error while adding attachment to the document. (23999)".
Looking at PDFCreator.log.txt (19.6 KB) (trace level activated), this error is raised because the pdf file used as attachment is password protected and no owner password is provided to the iText library (used internally by pdfcreator).

Performing the same operation through pdfcreator virtual printer instead of COM interface failed with the same error.
Performing the same operation (with COM interface and/or virtual printer) with a pdf file NOT password protected as attachment works correctly.

Is there a way to provide the pdf attachment's password to PDFCreator prior to call ConvertTo method ?
If it's not forseen to provide password for attachment, a bug report should be created :worried:

Many thanks in advance for your help.