All the volumes are searchable with Acrobat Reader. Each lesson title is also “bookmarked.” You will have to click on the bookmark tab on the left of your screen once the file loads.
Volume 19 was never printed in booklet form.
Volumes 1-18 (942 lessons) have a corresponding audio file. We are in the process of matching the audio files with the PDF file of that lesson.  With that many lessons, it is a work in progress. Check back often to see the updates.
We are working on a CD that will soon be available that puts all the volumes in one file making it easier to search the complete set. It also contains the commentary on ROMANS, the book of JUDGES and the book on the HOME.