Document loading functions are used to get handle document object. It may be early created PDF document located in file or in memory or newly created document. 

In any case user receives handle to PDF document object and may use all abilities to modify it. 

Functions of the document saving are used to store document modification results. 

We may store PDF document in file or in memory stream if we modified or created and filled in new document. 

It does not depend if we save or not document it must be closed if we loaded or created document. It gets correctly to finish work with PDF documents and release used memory.