Convert Excel formats to pdf - Powershell

I'm still new to powershell myself, so can't answer specifically what was causing the error, however I think I found the solution. It seemed to be with only the Excel conversion. The Word and PPT conversions worked flawless. I've changed the code for that portion and it seems to be working now:

$folderpath =  $(get-location) 
 Add-type -AssemblyName office
#Convert Word formats to pdf
$wdFormatPDF = 17
 $word = New-Object -ComObject word.application
 $word.visible = $false
 $fileTypes = "*.docx","*doc"
 $wordFiles = Get-ChildItem -path $folderpath -include $fileTypes -Recurse
foreach ($d in $wordFiles) {
 $path = ($d.fullname).substring(0,($d.FullName).lastindexOf("."))
 "Converting $path to pdf ..."
 $doc = $word.documents.open($d.fullname)
 $doc.saveas([ref] $path, [ref]$wdFormatPDF)
 $doc.close()
 }
$word.Quit()
#Convert Excel formats to pdf
$xlFixedFormat = "Microsoft.Office.Interop.Excel.xlFixedFormatType" -as [type] 
$excelFiles = Get-ChildItem -Path $folderpath -include *.xls, *.xlsx -recurse 
$objExcel = New-Object -ComObject excel.application 
$objExcel.visible = $false 
foreach($wb in $excelFiles) 
{ 
 $filepath = Join-Path -Path $folderpath -ChildPath ($wb.BaseName + ".pdf") 
 $workbook = $objExcel.workbooks.open($wb.fullname, 3) 
 $workbook.ActiveSheet.PageSetup.Orientation = 2
 $objExcel.PrintCommunication = $false
 $workbook.ActiveSheet.PageSetup.FitToPagesTall = $false
 $workbook.ActiveSheet.PageSetup.FitToPagesWide = 1
 $objExcel.PrintCommunication = $true
 $workbook.Saved = $true 
"saving $filepath" 
 $workbook.ExportAsFixedFormat($xlFixedFormat::xlTypePDF, $filepath) 
 $objExcel.Workbooks.close() 
} 
$objExcel.Quit()
#Convert Powerpoint formats to pdf
$ppFormatPDF = 2
 $ppQualityStandard = 0
 $p = new-object -comobject powerpoint.application
$p.visible = [Microsoft.Office.Core.MsoTriState]::msoTrue
 $ppFiletypes = "*.pptx","*ppt"
 $ppFiles = Get-ChildItem -path $folderpath -include $ppFiletypes -Recurse
foreach ($s in $ppFiles) {
 $pppath = ($s.fullname).substring(0,($s.FullName).lastindexOf("."))
 "Converting $pppath to pdf ..."
 $ppt = $p.presentations.open($s.fullname)
$ppt.SavecopyAs($pppath, 32) # 32 is for PDF
 $ppt.close()
 }
$p.Quit()
 $p = $null
[gc]::collect()
 [gc]::WaitForPendingFinalizers()