Ondrej Sevecek's Blog

# yes, turn this to $true if you want the script to do its job
# just a matter of security to look at the state of the matters first
$delete = $false

$site = get-spsite http://intranet.contoso.com

$site.RootWeb.ContentTypes | % { 
  
  $oneCT = $_
  $fieldsToDelete = $oneCT.Fields | ? { $_.InternalName -like '_dlc_DocId*' } | Select -Expand InternalName

  $fieldsToDelete | % { ([string] $_).Trim() } | ? { $_ -ne '' } | % {

    echo ('Deleting: {0} | {1}' -f $oneCT.Name, $_)
    
    if ($delete) { 

      $oneCT.FieldLinks.Delete($_)
      $oneCT.Update()
    }
  }
}

# 
# You must run the following part several times manually, because as we modify a field and .update() it
# the Fields collection gets updated and further enumerations are blocked with an exception
#

$site.RootWeb.Fields | ? { $_.InternalName -like '_dlc_DocId*' } | % { 

  echo ('Deleting: {0} | readOnly = {1} | hidden = {2} | allowDelete = {3}' -f $_.InternalName, $_.ReadOnlyField, $_.Hidden, $_.AllowDeletion)
  
  if ($delete) { 

    if ($_.ReadOnlyField) { 
 
      $_.ReadOnlyField = $false
      $_.Update()
    }

    if ($_.Hidden) {

      $_.Hidden = $false
      $_.Update()

    }

    if ($_.AllowDeletion -ne $true) {

      $_.AllowDeletion = $true
      $_.Update()
    }

    $_.Delete()
  }
}