This seems to work for me, although the use of Sendkeys is pretty much eschewed by the forum experts.
When the PDF printer dialog opens, just highlight the entire line and press Ctrl+v to paste in the path and file name.
Application.CutCopyMode = False 'clear clipboard
Dim cname, invnum
Dim fpath As String
fpath = "C:\Temp\" 'change this path per your requirements
Dim fname As Variant
fname = Range("D1").Text
cname = Range("A1").Value
invnum = Range("B1").Value
Range("D1").Value = fpath & cname & " " & invnum & ".pdf" 'change D1 to a cell of your choice
InputBox "clipboard", , Sheets("Sheet1").Range("D1").Text
Application.ActivePrinter = "doPDF v5 on DOP5:" 'change this line and the next to whatever PDF printer you use
Application.ActiveSheet.PrintOut Copies:=1, ActivePrinter:="doPDF v5 on DOP5:"