How can I get data of original document when I copy the document content to a new culture version?

If you copy the document content from another language in CMSDesk, you can get data of original document in the OnAfterInsertNewCultureVersion method of CustomTreeNodeHandler like:

string sourceDocumentId = HttpContext.Current.Request.QueryString["sourcedocumentid"];
TreeProvider treeProvider = (TreeProvider)tree;
TreeNode sourceNode = DocumentHelper.GetDocument(Convert.ToInt32(sourceDocumentId), treeProvider);