Batch file that adds the "ShrinkPDF" context menu

InstallShrinkPdf.cmd

@echo off

echo Installing the Shrink PDF shell extension

::Detecting gswin

where /q gswin64c.exe
IF ERRORLEVEL 1 (
    echo Cannot find gswin64c.exe. Make sure you've installed Ghostscript.
    echo You can install it with "choco install ghostscript".
    EXIT /B
)

:: Admin elevation code via https://stackoverflow.com/a/24665214/497403

:: Check privileges 
net file 1>NUL 2>NUL
if not '%errorlevel%' == '0' (
    powershell Start-Process -FilePath "%0" -ArgumentList "%cd%" -verb runas >NUL 2>&1
    exit /b
)

:: Change directory with passed argument. Processes started with
:: "runas" start with forced C:\Windows\System32 workdir
cd /d %1

for /F "tokens=* USEBACKQ" %%F in (`where gswin64c.exe`) do (
set gswin_path=%%F
)

echo Found gswin: %gswin_path%

reg ADD "HKEY_CLASSES_ROOT\*\shell\ShrinkPDF\command" /ve /t REG_SZ /d "cmd /c move \"%%L\" \"%%L.old.pdf\" & \"%gswin_path%\" -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dNOPAUSE -dBATCH  -dQUIET -sOutputFile=\"%%L\" \"%%L.old.pdf\" & del \"%%L.old.pdf\"" /f

echo All done

pause