In the Certified PDF workflow, all the modifications done in a PDF document are logged per session and saved in an edit log file. Also, the edited PDF documents can be saved incrementally. This means that the changes done in version 3, for example, can be saved “on top of” the changes done in version 2 but you keep one physical PDF file.
The incremental save principle does not necessarily increase the file size of your PDF document drastically because Adobe Acrobat only saves the changes made during the different sessions. The difference in file size may become apparent if you delete a large number of objects, because these objects are maintained in one or more versions. You can, however, at any stage in the workflow, “optimize” your Certified PDF document, i.e. reduce its file size, simply by using the Save As function of Adobe Acrobat and clicking the Certified Full Save button. You will still have a Certified PDF document with history information about previous editing sessions, but you will no longer be able to save snapshots of these sessions or use the roll-back mechanism to revert to a previous state of your Certified PDF document.