Beginning with PDFXv5, you can show or hide the progress window via the //PDFX,Saver.ShowProgress,<bool> directive; see Saver
PDFXv3 did not offer such an option, although you could set it globally by modifying the following registry setting manually:
HKEY_CURRENT_USER\Software\Tracker Software\PDF-XChange 3.0\Drivers\pdfSaver
Within this path, you can set the value of the HideProgressWindow field to 1 to hide the progress dialog for all PDFX printouts generated by the current user. To do this for all users on the current machine, use the equivalent path in the HKEY_LOCAL_MACHINE hive, i.e.:
HKEY_LOCAL_MACHINE\Software\Tracker Software\PDF-XChange 3.0\Drivers\pdfSaver
Note that the PDFX print progress dialog may appear redundant or confusing when A-Shell is also displaying its own printer abort dialog. (See the NOABORTDLG printer init command in the Setup Guide for information on disabling A-Shell's printer abort dialog.)