You can download the latest Pentaho Reporting software development kit (SDK) from http://reporting.pentaho.com.
The SDK is available as both a .tar.gz and a .zip archive; both contain the same files, but the .zip file format is more Windows-friendly, and .tar.gz is more Mac-, Linux-, and Unix-friendly.
Once downloaded, unpack the Pentaho Reporting SDK archive to a convenient and accessible location. If you use the Eclipse or IntelliJ IDEA development environments, this directory will also serve as your workspace.
In an effort to reduce the size of the SDK, the source code of its constituent libraries is not included. If you need to see the source to any of the software distributed with the Pentaho Reporting SDK, see Source Code Links for instructions.