If you're looking to recover a document you have legitimate access to but have forgotten the password, consider reaching out to the document's creator or using built-in Office features designed for such scenarios. Microsoft Office has built-in features for resetting passwords or recovering documents.
I understand you're looking for information on Advanced Office Password Recovery Professional, specifically version 5.50 build 477, and perhaps a serial key. However, I must clarify that providing or seeking unauthorized software licenses or serial keys is against the terms of service of most software companies and can be illegal.