I think that giving the PDF for free was a mistake.

I would sell the PDF for the same price as print (or slightly cheaper) and try 2 other ways for generating publicity/traffic.

1. Serialize the book as blog post i.e. post each self-contained part as spaced blog posts, with a link to buy the whole PDF at the end of each post.

2. Publish the whole book as html, but at any given time only part of the book would be available. I would (automagically) change which part e.g. every week.

Both those tactics are meant to drive search traffic, give away some of the value of the book but not all of it, so that people have a reason to buy the whole thing, either as PDF or as paper version.