I don't know of a simple way of doing this - although there may be one! By default, PDF writer generates the PDF file name based on the name of the Excel workbook. If your file is called BOOK999.XLS, then PDF writer will use that as the default name.
Are you looking for some different way of specifying a PDF file name, like creating your own "print" button?
Almost all printer settings, including the PDF converter's default filename, are controlled by the printer driver, not Excel. In most cases it is extremely difficult to change printer driver settings from Excel VBA. From what I can tell, the only solution involves using code to change registry settings, which should only ever be done with caution, and on most corporate computers these days you won't have been given enough system permissions to be able to do it at all.
Note I don't know the specific PDF converter that you refer to, so it's possible that it's an exception to this - try looking for help from the web site of the company that makes the PDF converter.
However, if you want to bypass the printer dialog box completely, you can do it using the PrintOut method. I'll give two examples, one which assumes that you are using the default printer, and another that sets the printer.
Example 1 - uses default printer
' Set the default filename
sFileName = "YourFullPathAndFileName.pdf"
' Use the PrintOut method to generate the file
ActiveWindow.SelectedSheets.PrintOut Copies:=1, _
PrintToFile:=True, PrToFileName:=sFileName
Example 2 - sets the printer (see extra notes at end of this post)
' Set the default filename
sFileName = "YourFullPathAndFileName.pdf"
' Define the printer to use
sPrinterName = "Put your pdf printer name here exactly as it appears in your printers list"
' Set that printer as Excel's default
Application.ActivePrinter = sPrinterName
' Use the PrintOut method to generate the file
ActiveWindow.SelectedSheets.PrintOut Copies:=1, _
ActivePrinter:=sPrinterName, _
PrintToFile:=True, PrToFileName:=sFileName
If you still want a dialog box that asks for the filename, you can do that by putting the following code after the sFileName= line and before the PrintOut line:
' Call a SaveAs dialog box
sFileName = Application.GetSaveAsFilename(InitialFileName:=sFileName, _
fileFilter:="Adobe Acrobat (*.pdf), *.pdf")
' Stop the macro if the dialog box is cancelled or the filename is blank
If sFileName = False Then
Exit Sub
End If
The drawback to using the PrintOut method is that you won't be able to change any of the other settings that you can normally change from the printer driver dialog box (such as page size).
Hope this helps.
Notes on Example 2:
If you're trying this method, I've found the best way to get the printer name exactly right is to record a macro that prints to that printer, and then copy and paste the printer name as it was recorded. On a network, the printer names can vary from user to user. There's probably a workaround for that, but I don't know it. If anyone wants to suggest one, I'd welcome it! The "Application.ActivePrinter =" line should be redundant because the PrintOut method should use its own ActivePrinter:= setting. However, I have found that occasionally Excel decides to use the default printer instead (I haven't figured out why), so having that extra line helps stop that.