This PowerShell script is for propagating legacy Document IDs into SharePoint. This is great if you are moving existing documents to SharePoint where you want to retain the Document Id. SharePoint let’s you configure the format of Document Id’s so that going forward any new documents will have a consistent format. For more info on configuring the Document Id format see Tobias Zimmergren’s great article. Where this script comes in, is that you can retain the existing document id on these document as they are migrated into SharePoint, should help keep users happy. All credit for the script goes to Joel Plaut.