$applyChanges = $false;
$testPass = $true;
$documentTemplateUrl = "Library/Forms/template.xsn"

$web = Get-SPWeb http://Server/Sites/Site
if ($web -eq $null)
{
                "web not found";
                return;
}
$listName = "Library";

$list = $web.Lists[$listName]
if ($list -eq $null)
{
                "List $listName not found";
                return;
}

$newTemplateUrl = [Microsoft.SharePoint.Utilities.SPHttpUtility]::UrlPathEncode($web.Site.MakeFullUrl($documentTemplateUrl), $true);

Write-Host "Content Type document template url = " $newTemplateUrl;

$spQuery = New-Object Microsoft.SharePoint.SPQuery
$spQuery.ViewAttributes = "Scope='Recursive'";
$spQuery.RowLimit = 500
$caml = '<OrderBy Override="TRUE"><FieldRef Name="ID"/></OrderBy>' 
$spQuery.Query = $caml 

do
{
    "Getting item batch"
    $listItems = $list.GetItems($spQuery)
    $spQuery.ListItemCollectionPosition = $listItems.ListItemCollectionPosition
    foreach ($item in $listItems)
    {
                                Write-Host "Item ID = " $item["ID"];

                                if ($item["TemplateUrl"] -ne $newTemplateUrl)
                                { 
                                                $oldurl = $item["TemplateUrl"]
                                                $item["TemplateUrl"] = $newTemplateUrl;

                                                if ($applyChanges -eq $true) 
                                                {
                                                                   Write-Host "Changing " $oldurl " to " $item["TemplateUrl"]
                                                                  $item.SystemUpdate();
                                                }
                                                else
                                                {
                                                                                Write-Host "Would change " $oldurl " to " $item["TemplateUrl"]
                                                }
                                }
    }
                if ($testPass -eq $true)
                {
                                "Test pass complete";
                                break;
                }
}
while ($spQuery.ListItemCollectionPosition -ne $null)