Users get lost inside PDF files, which are typically big, linear text blobs that are optimized for print and unpleasant to read and navigate online. PDF is good for printing, but that's it. Don't use it for online presentation.
Two points to remember:
- All big linear text blobs are unpleasant to read and navigate online. PDF's allow you to print them and read them offline where they are more bearable.
- For some reason when people say online presentation I think of Powerpoint or Flash. I have never seen Acrobat used for an online presentation. If this is a widespread problem I have somehow missed it.