Is PDFCreator Multi-Thread

I need to generate 6 kinds of report in PDF from Excel and Word.

I find that if I run the 6 report process in parallel, each process will use 1 instance of PDFCreator, I find that the report generated may be mixed.

That is report 1 content will be report 2 content which is wrong.

It seems that the report content are corrupted or mixed.  Is PDFCreator multi-threading ?  Or I need to generate the report one by one ?  Is it due to the spool file mixed ?

Please suggest...