How do you ship the documentation for your product, HTML or PDF?
PDF is great if users want to print all the documentation, but PDF is more or less useless for online presentation. I usually find it very frustrating reading large PDF documents online and I tend to get lost while reading the documentation.
HTML is much more flexible when reading documentation online, but a problem with HTML is that a document usually contains a number of HTML files and images. Non technical users might have a hard time unpacking and reading the documentation.
BarracudaDoc is a tool that unifies all HTML and images etc. into one file. The tool creates a small Web-Server with the documentation embedded into the executable. The Web-Server automatically opens an instance of the users default browser, when started, and directs the browser to index.html in the root of the documentation.
Jakob Nielsen has great lab quotes on why users hate PDF.