The JDBC Adaptor is not a reporting tool, it allows third party products include TIBCO JasperSoft Studio Professional to connect to the database.
The JDBC driver is only used to run the reports, or to Data Preview from the Dataset window, when using TIBCO JasperSoft Studio Professional. Technically, you don't need JDBC to undertake as most of my JasperSoft development I do not use the JDBC driver, just publishing to the JasperSoft server and running from the server (each to their own on how to develop, just quoting what I do).
Regardless of the above, I do have the JDBC installed. In my case, I placed them into a folder not in the Workspace, and just used the full path name when configuring the Data Adaptor in JasperSoft.
You do have to make sure you have the correct JDBC URL, as well as the correct username/password (jaspersoft username/password, not your PPM account), but the JDBC drivers do work.