Many times, System Administrators will gauge the effectiveness of their Synergy set-ups, especially workflow and documents. A good report on Document types (with their total number of documents per type) within Synergy can be found under Documents / Reports / Statistics / Document Type. Quickly you can see which Document types are being used by your organization with both a line graph and document totals.
To see which of your employees are creating these documents, I would suggest using the Pivot Analysis for Documents located at Documents / Reports / Documents / Pivot Analysis. Have the Row function display Type (of Document) and the column to display the Creator.
Using these reports will help you manage the use of existing document types and aid in creating new types based upon business requirements.