@echo off

set Where=C:\Users\user1\Desktop\Scan\

setlocal enabledelayedexpansion
set count=0
for /f %%e in ('"dir /a-d/b "%Where%*_Scan*.pdf" 2>nul"') do (
 set name=%%~ne
 set number=!name:*_Scan=!
 if !number! gtr !count! (
  set count=!number!
  )
 )

:loop
for %%f in ("Z:\*.pdf") do (
 set /a count+=1
 move "%%f" "%Where%%date:~6,4%%date:~3,2%%date:~0,2%_Scan!count!.pdf">nul
 )
ping -n 10 localhost>nul
goto loop

:test
:loop
if exist Z:\*.pdf goto go
ping -n 10 localhost
goto test
:go
copy Z:\*.pdf C:\Users\user1\Desktop\Scan\
Set Where=C:\Users\user1\Desktop\Scan\
FOR %%f IN ("%Where%\*.*") DO ren "%%f" "%Date:~6,4%%Date:~3,2%%Date:~0,2% %%~nxf"
del /q Z:\*.pdf
ping -n 10 localhost
goto loop