Free PDF reader apps

Below are the free PDF reader apps I'm trying out. Each one also gets its own separate blog entry, into which incremental updates will flow over time. If I ever feel those entries are sufficiently mature, I may make a chart comparing all of these apps.

7/2/11: I only rarely use PDF files on my iPod, and my focus to date has been on those typically having 2 or 3 columns in portrait orientation. PDF files having no columns will typically need to be read in landscape orientation for the text to be big enough to read; I'm not sure yet how much I will eventually cover that type of usage. I have also since loaded more PDF-reading apps on my iPod, but to date I have looked at those even less than the few I list below.

• Dropbox (whose main functionality is to allow sharing of files over the web after you make an account, but which has a built-in PDF reader)
• iPDF
• PDF Reader Lite by Kdan Mobile Software LTD (my favorite)