如何批量导出Powerpoint To PDF 文件 How to export all ppt files in a folder to pdf by powershell

最近有个需要要导出很多PPT，PPTx文件为PDF，因为我的手机不支持查看ppt,但是查看PDF很方面，可以进行PDF上的文字搜索等等。但是手动另存为PDF也是一个很累人的活，为了图方便，查阅了相应文档，写出了下面一个简单的powershell script

关于导出类型，导出PDF的值常量为32，其他导出类型见下面MSDN http://msdn.microsoft.com/en-us/library/bb251061(office.12).aspx

param(
    [string]$folder=$(throw("Input the path of folder which contains ppt to export to pdf "))
)

function ExportToPDF($path){
    $newname=$path -replace "\.[^.]*$",".pdf"
    "exporting $path to $newname "
    if(-not (Test-Path $newname)){
        $b= $a.Presentations.open($path)
        $b.SaveAs($newname,32)
        $b.close()
    }
}

while( -not (Test-Path $folder)){
    $folder=Read-Host -Prompt "input folder path:"
}

    Add-type -AssemblyName office
    Add-Type -AssemblyName microsoft.office.interop.powerpoint
    $a= New-Object -ComObject powerpoint.application
    $a.Visible=[Microsoft.Office.Core.MsoTriState]::msoTrue
    Get-ChildItem -Path $folder  -Include "*.ppt", "*.pptx" -Recurse |%{
        exporttopdf $_.fullname
    }

$a.quit()
$a = $null
$b= $null
Remove-Variable "a" -Force
Remove-Variable "b" -Force
[gc]::collect()
[gc]::WaitForPendingFinalizers()