This post is here for personal reference and was adapted from this link.
The following script allows you to convert a directory of Powerpoint slides into a set of PDFs. I found this particularly useful when I was revising some materials at work that I needed to access from my Android phone.

## Instructions

1. Open PowerShell
2. Navigate into the directory that contains all of your PPTX files
1. Set-Location path\to\pptx\folder
3. Run the following script:
$ppt = New-Object -com powerpoint.application$opt = [Microsoft.Office.Interop.PowerPoint.PpSaveAsFileType]::ppSaveAsPDF
Get-ChildItem '.' -Filter '*.pptx' | ForEach-Object {
$ifile =$_.FullName
$pres =$ppt.Presentations.Open($ifile)$pathname = split-path $ifile$filename = Split-Path $ifile -Leaf$file = $filename.split(".")[0]$ofile = $pathname + "\" +$file + ".pdf"
$pres.SaveAs($ofile, \$opt)
}


You might also try adding -Parallel option to the ForEach-Object block to increase performance.