Get all pages located in "Pages" library and change theirs page layout.

UpdatePagelayout.ps1

# ----------------------------------------------
# Author: Romain Blanchard
# Date: 20.06.2012
# Description: Get all pages located in "Pages" library and change theirs page layout.
# ----------------------------------------------

Add-PSSnapin Microsoft.SharePoint.PowerShell -erroraction SilentlyContinue


# Variables
$spweb = Get-SPWeb -Identity "http://rbla-sp2010-002/sites/migration/audit/"

$spPubWeb = [Microsoft.SharePoint.Publishing.PublishingWeb]::GetPublishingWeb($spweb)
$pages = $spPubWeb.PagesList
write-host ""

foreach($item in $pages.Items)
{
  $pubPage = [Microsoft.SharePoint.Publishing.PublishingPage]::GetPublishingPage($item)
  $url = new-object Microsoft.SharePoint.SPFieldUrlValue($pubPage.ListItem[[Microsoft.SharePoint.Publishing.FieldId]::PageLayout].ToString())
  if($url -ne $null)
  {   
    $newurl = new-object Microsoft.SharePoint.SPFieldUrlValue("http://rbla-sp2010-002/sites/migration/_catalogs/masterpage/BlankWebPartPage.aspx, Blank Web Part page") #Location, Title
	write-host "Page : $pubPage.Name" -foregroundColor Yellow
	$pubPage.CheckOut()
	$pubPage.ListItem[[Microsoft.SharePoint.Publishing.FieldId]::PageLayout] = $newurl
	$pubPage.ListItem.UpdateOverwriteVersion() 
	$pubPage.ListItem.File.CheckIn("Page layout fixed.", [Microsoft.SharePoint.SPCheckinType]::MajorCheckIn);
  }
}

write-host ""
write-host "-----------------"
write-host ""
write-host "Done." -foregroundColor Green