The Output file list dialog will display before the PDF files are created when One File per Page is checked in the General Settings tab. The Output file list dialog gives you additional control over the naming of the PDF files as they are created.
Use layout name - Use the layout name for the PDF file name.
Use page number - Append the page number to the end of the PDF file name.
Use file name - Added the Revit file name to the begging of the PDF file name.
Prefix - Type text to add to the beginning of the PDF file name.
Suffix - Type text to add to the end of the PDF file name.
Example showing naming with Use page number, Prefix and Suffix defined
Example showing file naming with Use page number and Use file name
