With the release of TWiST 6.4 DALiM has changed the behavior of the CreatePages, making it much more flexible.

Now you can use the tool to trim an incoming PDF without normalizing it, thus you can change the trim of the incoming PDF without changing anything else,  so you could then do your preflighting and normalizing in the PsCheck.

Depending on how you configure the CreatePages tool you can change the nature of the file after the tool:
• Activate the keep PDF option:

            If the Object Merge Option IS active the incoming file stays a PDF but is trimmed and Normalized.

            If the Object Merge Option is NOT active the incoming file stays a PDF is trimmed but is NOT Normalized. This means TWiST only modifies the Trim table info in the PDF, it does not modify or change the PDF data.

• Disable the Keep PDF option:

            If the Object Merge Option IS enabled it interprets the incoming file converting it to a pgs, it does not keep a copy of the original PDF in the .inprocess directory

 If the Object Merge Option is NOT active the incoming it does not really convert or normalize the file to a pgs, just nests a copy of the PDF inside a dalim page, keeping a copy of the original PDF.