The lead document field is where you would upload the document/form/filing you are wanting to submit to the court.
In general, if there is a filing code that matches the document you need to file, your document should be filed as a lead document. Only lead documents get a file stamp. Each document that requires a file stamp must be uploaded as a separate lead document with its own filing code.
Note: Do NOT make each page of a document/form into its own PDF. A document you file should be one PDF file.