can we use get document property function to batch the document together as a single flat file ?
Document properties are used for various purpose. They are not used to batch documents. To batch documents you can use Flow Control and to combine documents as single file you can use DP. I am not sure what is your requirement.
You can read more about Document properties in below article
Getting and setting document properties in the Connector SDK
When you pull files then all files are pulled and given out of the connector shape as output.
Once you get it Use Flow Control shape to initiate batch with different threads.
Although you can specify batch count after you split any specific data is available in Data process shape.
All the above has nothing to do with Document properties
Retrieving data ...