Below is a structure of QPDFSamplesViewer, a sample project using qoppapdf.jar, Android Qoppa’s PDF toolkit, within Eclipse.

Download qpdftoolkit.zip which includes qoppapdf.jar, libs and assets folder
Download qPDF_Samples_Viewer.zip

Make sure that the libs folder and the assets folder are in the correct location so that they are available as resources.

location of libs folder in Eclipse
Note the location of libs folder and the assets folder