Get Number of PDF Pages (Greater than 1) Parallel with Throttle Limit

getNumberOfPdfPages.ps1

$ArrayList = [System.Collections.ArrayList]@()
# Note: this scripts searches for folders named "Single" recursively from the starting folder.
Get-ChildItem -Path .\ -Recurse | Where-Object {
    $_ -is [System.IO.FileInfo] `
    -and ($_.Directory.Name -eq 'Single')
} | ForEach-Object {
    $ArrayList.add($_.FullName)
}

# Threaded task to use pdfk to get files. 
workflow Test-Workflow{
    param(
        [Parameter (Mandatory = $true)]
        [System.Collections.ArrayList]$ArrayList
    )
    
    # Multithreaded - that was easy. 
    ForEach -Parallel -throttlelimit 5 ($file in $ArrayList)
    {
        $command = '"E:\Program Files (x86)\PDFtk Server\bin\pdftk.exe" "'+$file+'" dump_data | findstr NumberOfPages'
        $output = iex "& $command"
        $pages = $output.Substring(15,$output.length-15)
        
        # Only output files with more than one page. (These files were supposed to be "single" page pdfs)
        if($pages -gt 1){
          Write-Output $file $pages
        }
        # Write-Output $output
    }
}

Test-Workflow -ArrayList ($ArrayList)
Write-Host "Press any key to continue ..."

$x = $host.UI.RawUI.ReadKey("NoEcho,IncludeKeyDown")
Write-Host "Finished"