When you export to 2D or 3D DWF, a unique, consistent ID is generated for each object. This ID consists of the GUID (Globally Unique Identifier) and the element ID. This ID scheme virtually eliminates duplicate element IDs when DWF files are merged from multiple sources outside Revit.
When you export object data to 2D DWF, any property with an assigned unit of measurement exports user-visible and invisible information. User-visible information consists of formatted values. Invisible information consists of 2 additional fields: an unformatted, raw value, and a field that describes the unit type or data type.